Search  for anything...
Optimum Nutrition

Optimum Nutrition Serious Mass Weight Gainer Protein Powder, Vitamin C and Zinc for Immune Support, Vanilla, 12 Pound (Packaging May Vary)

Based on 39,351 reviews
Condition: New
Checking for the best price...
$81.64
Save $2.35 was $83.99

Buy Now, Pay Later

As low as $13.61 / 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

Non-returnable due to Food safety reasons

View our full returns policy here.

Availability: In Stock.
Fulfilled by Amazon
Arrives Saturday, Oct 31
Order within 12 hours and 29 minutes

Available payment plans shown during checkout

Protect Your Purchase

Easy claims online, fast replacements, no fees

Checking for protection plans...

Recently Viewed

At a glance

Condition
New
Flavor
Vanilla
Size
12 lb (Pack of 1)
Dimensions
11.5 x 5.5 x 16 in; 12 lb
Weight
192 oz
Material Type Free
Caffeine Free

Features 7

  • Packaging may vary - New look, with the same trusted Quality!
  • Product Note: Exposure to heat or sunlight may lead to melting/damage of product. Hence customers are expected to be available during the product delivery
  • High Calorie Weight Gainer: 1,250 Calories per 2-Scoop Serving
  • 50 Grams of Protein per Serving

Description

More calories. More protein. More carbs. SERIOUS MASS by Optimum Nutrition serves up 1,260 calories, 50g of blended protein, and over 250g of carbohydrates per serving to help you maximize your daily caloric intake – the ideal post-workout and between meals shake for sizing up your goals. SERIOUS MASS provides you with more tools to help you pack on pounds, when taken in addition to normal calorie intake and over time with regular resistance training. Calories per gram: Fat 9, Carbohydrate 4, Protein 4.

Specs 9

Brand Optimum Nutrition
Flavor Vanilla
Servings per Container 16.0
Item Weight 192 Ounces
Material Type Free Caffeine Free
Product Dimensions 11.5 x 5.5 x 16 inches; 12 Pounds
Item model number 1031920
Department GNC|ALL|ALL|NUTRITIONAL SUPPLEMENTS

Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Saturday, Oct 31

This item is non-returnable:

Non-returnable due to Food safety reasons

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

So good, worth price !
Flavor Name: Vanilla Size: 6 Pound (Pack of 1)
I picked this a couple of summers ago to help keep weight on me. I tend to lose a lot of weight in the summer because I work outside a lot. This year was no exception and this stuff is absolutely amazing! It mixes up so well, I can work out with it, which helps build muscle, it helps my energy level levels., The ingredients are everything you need in a daily supply and the taste is great. I always mix mine with frozen fruit or peanut butter.! ... show more
Reviewed in the United States on July 9, 2025 by Casey
Amazing Powder
Flavor Name: Vanilla Size: 6 Pound (Pack of 1)
Loved The Taste It’s So Good & It Work Great Just mix it in your shake, I use bananas, peanut butter, milk, and oats
Reviewed in the United States on September 9, 2025 by Karilee
Reliable Weight Gainer That Works – I Keep Buying It
Flavor Name: Vanilla Size: 6 Pound (Pack of 1)
I’ve been using Optimum Nutrition Serious Mass for a while now and keep coming back to it because it delivers consistent results. It’s a great weight gainer with plenty of calories and protein to help me build muscle and add mass. The added creatine is a nice bonus, supporting my strength gains and recovery. The taste mixes well and isn’t too sweet or chalky, which is a plus compared to other mass gainers I’ve tried. If you’re looking for a dependable product to help with weight gain and muscle building, I’d definitely recommend Serious Mass. I’ve bought it over and over again and plan to keep doing so! ... show more
Reviewed in the United States on July 13, 2025 by James O'Malley
Good but voluminous
Flavor Name: Chocolate Size: 16 Servings (Pack of 1)
Tastes good and delivers great macros however the quantity you need to consume a single serving is massive If you want to blend two heaping scoops, which is one serving, and want to drink something that's less solid than concrete, you'll need to drink 5 or 6 pint glasses of this stuff. This isn't a quick, easy, dense way to get 1500 calories. It's a tremendous effort. I'm sure the ON mix is cleaner, but you can get easier calories with a 16" steak and cheese sub, and be less full. ... show more
Reviewed in the United States on August 18, 2025 by Timothy F. Webster
Value for money
Flavor Name: Chocolate Size: 16 Servings (Pack of 1)
Review Image by Joel Mills Joel Mills
Quality, dissolves easily, Taste is great. Love it already. Packaged properly.
Reviewed in the United States on August 29, 2025 by Joel Mills Joel Mills
Great results
Flavor Name: Chocolate Peanut Butter Size: 12 Pound (Pack of 1)
Highly recommend serious mass , I’ve been using it for 2 years, the results are fantastic. With serious weight training.
Reviewed in the United States on September 16, 2025 by JC is the answer
This stuff actually works
Flavor Name: Vanilla Size: 12 Pound (Pack of 1)
Bought this for my girlfriend to help her out some weight on and it has worked well so far. She loves the taste we mix ours in a ninja blender so its like a milkshake. We use whole milk and add peanut butter to up the calories and protein content. Plus it's a 12 pound bag it's huge and it works enough said it works. ... show more
Reviewed in the United States on August 21, 2025 by Dustin nielsen
Mixed Feelings — Helped Me Gain Weight but Caused Breakouts & Bloating
Flavor Name: Vanilla Size: 6 Pound (Pack of 1)
Review Image by Haneen Haneen
This is the first time I’ve actually finished a full container of a mass gainer, and while it helped me gain about 5 lbs (alongside eating more), I had some struggles with it too. I got the vanilla flavor, and it was extremely sweet—to the point where it felt like a sugar coma every time I drank it. I normally don’t eat sweets, so I believe this sudden sugar intake caused a noticeable acne breakout on my face. Like most gainers, it’s heavy on the stomach and made me feel bloated for hours, which made it hard to eat proper meals after having a shake. That said, it does mix very well with no clumps, and the texture is smooth and creamy. I’m not sure if vanilla is just the sweetest flavor, but I’m hesitant to repurchase unless I try a different one or find a cleaner option. It works, but there are trade-offs. ... show more
Reviewed in the United States on May 11, 2025 by Haneen Haneen
How it works
Checking for best price...