Search  for anything...
Serta

Serta ThermaGel 3-Inch Gel Memory Foam Mattress Topper, King

  • Based on 10,592 reviews
Condition: New
Checking for the best price...
$119.99 Why this price?

Buy Now, Pay Later

As low as $20.00 / mo
  • – 6-month term
  • – No impact on credit to apply
  • – Instant approval decision
  • – Secure and straightforward checkout

Ready to go? Add this product to your cart and select a plan during checkout.

Payment plans are offered through our trusted finance partners Klarna, Affirm, Afterpay, Zip, Apple Pay, and Google Pay. No-credit-needed leasing options through Acima may also be available at checkout.

Learn more about financing & leasing here.

Selected Option

Free shipping on this product

FREE 90-day refund/replacement

To qualify for a full refund, items must be returned in their original, unused condition. If an item is returned in a used, damaged, or materially different state, you may be granted a partial refund.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

Availability: In Stock.
Fulfilled by Amazon
Arrives Saturday, Aug 29
Order within 23 hours and 33 minutes
Available payment plans shown during checkout
Protection Plan Protect Your Purchase
Checking for protection plans...

Recently Viewed

Size: King 79"x75"


Set name: 3 Inch


Features

  • 100% Memory Foam
  • STOP SLEEPING HOT ACROSS YOUR FULL KING BED: Cooling gel-infused memory foam pulls body heat from the entire King sleep surface all night , a meaningful benefit for couples or hot sleepers. ThermaGel cooling dissipates heat.
  • DEEP PRESSURE RELIEF: 3 inches of contouring memory foam delivers deep plush feel and substantial cushioning at the hips, shoulders, and lower back across the full King width for back pain relief and restorative sleep.
  • SOFTENS A FIRM OR AGING KING MATTRESS: This thick gel memory foam mattress topper conforms closely to the body and extends the life of an older King mattress, without replacement cost.
  • BUILT TO TRUST: CertiPUR-US certified foam, made in the USA, with ventilated, breathable design. Tested for low VOC emissions, durability, and content safety. Sized 75 x 79 inches for standard King bed frames, platform beds, and adjustable bases.
  • IDEAL FOR PRIMARY BEDROOMS WHERE BOTH PARTNERS NEED COOLER, DEEPER COMFORT: A reliable thick King mattress topper for couples. Pair under a standard fitted sheet. Add to cart and experience the comfort tonight.

Description

"Sleeping hot or dealing with pressure discomfort on your King mattress? The Serta ThermaGel 3-Inch King Gel Memory Foam Mattress Topper delivers targeted cooling and deep pressure relief across the full width of your bed. The ThermaGel-infused foam actively dissipates body heat to keep the sleep surface cooler and more comfortable throughout the night , a meaningful benefit for couples or single sleepers who tend to sleep warm. At 3 inches, the topper conforms precisely to the body's natural curves, cushioning the hips, lower back, and shoulders for back pain relief, deeper plush feel, and more restorative sleep across the full King width. Ventilated, breathable construction supports airflow for all sleep positions. Made in the USA with CertiPUR-US certified foam for trusted safety, durability, and low emissions. Softens a firm or aging King mattress and extends its useful life. Designed for standard King bed frames, platform beds, and adjustable bases, this thick mattress topper layers seamlessly under existing bedding with no additional setup required. Upgrade your King bed today. Add to cart and experience cooling, pressure-relieving comfort from Serta ThermaGel. ThermaGel is a trademark of Leggett & Platt, Inc."

Brand: Serta


Color: Blue


Size: King 79"x75"


Fabric Type: 100% Memory Foam


Special Feature: Breathable, Cooling, Durable, Premium, Pressure Relief


Brand Name: Serta


Age Range Description: Adult


Model Name: ThermaGel


Number of Items: 1


Manufacturer: Elite Comfort Solutions


UPC: 094325278879


Manufacturer Part Number: 12275


Model Number: 12275


Unit Count: 1.0 Count


Item Type Name: Serta ThermaGel Memory Foam Mattress Topper


Other Special Features of the Product: Breathable, Cooling, Durable, Premium, Pressure Relief


Closure Type: Pull On


Water Resistance Level: Not Water Resistant


Fabric Type: 100% Memory Foam


Product Care Instructions: Spot Clean Only


Material Type: Memory Foam


Size: King 79"x75"


Item Display Dimensions: 3 inches


Color: Blue


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Saturday, Aug 29

Yes, absolutely! You may return this product for a full refund within 90 days of receiving it.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

  • Klarna Financing
  • Affirm Pay in 4
  • Affirm Financing
  • Afterpay Financing
  • Zip Pay in 4
  • Financing through Apple Pay
  • Financing through Google Pay
Leasing options through Acima may also be available during checkout.

Learn more about financing & leasing here.

Similar Products

Top Amazon Reviews

    • Queen that's bigger than a King Queen that's bigger than a King
Size: Queen 79"x59" Set name: 3 Inch
Review Image by Ashley
Review Image by Ashley
Review Image by Ashley
***Edit 05/09*** I realized after rolling and stuffing the topper back into its original box that the topper I received was for a California King. Make sure before you open this thing the sticker reads the size you purchased. Now I will say I received a replacement the very next day and I was able to sleep on it last night. I am changing my 2 🌟 review to a 5 🌟 because of how quickly they replaced it and being able to sleep on it, it was really comfy and I slept so well. My bed is 9 years old but there isn't anything wrong with it, it's just not as comfortable anymore. My boyfriend always complained My bed was too hard and made his back hurt and he said he slept so much better on this 3" mattress topper. This mattress topper is humongous. I ordered a Queen and once it fluffed out it measured way larger than the Queen measurements listed. It's like 85×75. It measures larger than the King sized measurements. It looks ridiculous on my bed and I would have to fold it over the edges or cut the foam for it to fit properly. I'm going to attempt to fold and roll this thing back up to send it off for a smaller size. I will say when I laid on it with the sheets it did feel soft and cool. Fingers crossed the full sized bed isn't too small. ... show more
Reviewed in the United States on May 7, 2026 Reviewed in the United States on May 7, 2026 by Ashley
    • Doesn't seem to run hot!
Size: King 79"x75" Set name: 3 Inch
Package arrived on time and was well packed. We removed it from paking and removed shipping plastic, then allowed it expand per the instructions. It had no offensive odor at all; in fact it was a pleasant smell if anything. The next day we placed it onto our mattress (it was easy to placeand it stays in place well), put the sheets on, and at bedtime we climbed in. The topper provided an excellent mixture of softness and support. It has not run hot at night and is very pleasant to sleep upon. It appears to be a very durable topper. ... show more
Reviewed in the United States on June 15, 2026 by Mike Oberski
    • Better Than Most Other One's
Size: Twin XL 79"x38" Set name: 2 Inch
I have tried several cushions for my well used recliner. The SertaThermaGel Cooling -Memory foam oneI just bought is the most comfortable one yet. It is not even two inches thick,,but does the job wonderfully without sinking in too much like old car seats. I do put a pillowcase over it for sleeping. It needs a cloth cover. It has a plastic feeling one.It does not slip and I don't always cover it.I would call this one supportive and somewhat cooling ... show more
Reviewed in the United States on June 14, 2026 by Meckanic
    • Like sleeping on a cloud – a perfect refresh for my mattress! ⭐⭐⭐⭐⭐
Size: Full 74"x53" Set name: 3 Inch
I bought this Serta ThermaGel topper (3-inch, Full size) to add some life to an older mattress that was starting to feel a bit too firm and lumpy. I wanted something that would offer pressure relief without making me overheat, and this has been a fantastic upgrade. Pros: Instant Comfort Upgrade: The 3-inch thickness is substantial. You definitely sink into it, but it feels supportive rather than just squishy. It significantly reduced the pressure points on my hips and shoulders. Cooling Effect: I tend to sleep hot, so I was hesitant about memory foam. However, the "ThermaGel" technology actually seems to work. It feels breathable and stays cooler than standard yellow foam toppers I've used in the past. Brand Quality: It’s nice to see it’s "Made in the USA." The foam feels dense and durable, not cheap or flaky. It expanded to its full shape pretty quickly after unboxing. No Slip: The texture of the foam seems to grip the mattress well enough that it doesn't slide around too much under the fitted sheet. Cons/Things to Note: Initial Smell: Like almost all memory foam products, it had a slight "new foam" smell right out of the box. I let it air out for about 24 hours before putting sheets on it, and the smell went away completely. Care: The instructions say "Spot Clean Only," so I highly recommend using a waterproof or thick mattress protector over it just to keep it clean, as you can't throw this in the washing machine. Verdict: If you aren't ready to buy a brand-new mattress but need better sleep quality, this is a very cost-effective solution. It turned a mediocre bed into a luxury feel. ... show more
Reviewed in the United States on December 2, 2025 by DPM
    • Great value Great topper!! Great value Great topper!!
Size: King 79"x75" Set name: 3 Inch
Review Image by TAMMY T
Review Image by TAMMY T
EXACTLY what i wanted. My family bought me a similar Serta topper 5 yrs ago after a major surgery. My matress has seen better days. The first one was very comfortable and I was still using it but my large dog digs at the bed before laying down and did rip it. Honestly, the first one was a little too soft. I had a full open abdominal so those muscles were cut and I have bad joints , so sitting up can be tricky. I found you sink in and had to actually roll to get up. This Serta topper is much more comfortable & much easier to get up from because all though soft, it is firmer. It bounces right back after you get up. . It gives but doesn't make you sink. This helps sleeping when you have joint pain. I didnt feel as hot with it as much as the first either but could just be me. It came in a solid box ,( grandkids LOVE the box with the sheep and large flaps lol) compressed, well wrapped and in a duffle bag. It was fully expanded as soon as I opened it. I didnt notice any smells. This was the best sleep I've had in a long time and at this price I've considered buying an extra when it inevitably rips and wears down but I've read some reviews online that toppers didn't fully expanded after stored a long time. Ill just enjoy this till it dies and replace it then. It was very fast shipping also. I HIGHLY RECOMMEND THIS & WILL buy again! ... show more
Reviewed in the United States on September 27, 2025 Reviewed in the United States on September 27, 2025 by TAMMY T
    • Need a mattress pad? This is the one.
Size: Queen 79"x59" Set name: 3 Inch
I like it. I’ve slept way more comfortably since I put it on my bed. Looks nice. I let it air out and sit for a day before putting it on my bed and it doesn’t smell bad at all. Not hot. Seems durable. I rotate my mattress every two weeks and it stays nice.
Reviewed in the United States on June 23, 2026 by Phoenix Gomez
    • Comfortable for our grandkids
Size: King 79"x75" Set name: 3 Inch
Very nice! Works well . Grandkids love it
Reviewed in the United States on July 7, 2026 by Freddie Sullens
    • Fit with an inch or so to spare
Size: King 79"x75" Set name: 3 Inch
My decades old Posturepedic mattress was taking a toll on my back. It is just too firm for me to sleep comfortably so I needed help. This 3-inch mattress topper helps. It relieves the stress on my spine caused by my rock-hard mattress and provides some pain relief when I am on my side. Its durability is yet to be determined. The topper feels cool to the touch but after lying on it for a while there is a warmth that seeps through. This might be a function of the topper cover that I bought separately, or it could be a function of the memory foam itself. This is not a deal breaker although I live in the tropics. I think it is value for the money spent. So far, so good. It came nicely packaged in its own bag, a pleasant surprise. It is a tad too soft but has enhanced by sleep quality. Probably a 4-inch topper would have been just perfect, but this works okay. There was a faint "new" smell when the memory foam was laid out to air but that has gradually faded. It seems to bounce back to its original thickness after sleeping on it. Overall, it has provided some softness to a too-firm mattress, which was the purpose of getting it. Durability is yet to be determined. ... show more
Reviewed in the United States on September 18, 2025 by JBF

Can't find a product?

Find it on Amazon first, then paste the link below.
Checking for best price...