Serious Mass Weight Gainer
Optimum Nutrition

Serious Mass Weight Gainer

Protein Powder Weight Gainer*
Loaded with 1,250 Calories, 50g of Protein, & 25 Vitamins and Minerals to Pack on Pounds*
8.6  out of 10  (1,154 Reviews)
Save 20%
Order and automatically receive 20% Off in your cart on Serious Mass Weight Gainer!

Save an additional 10% off as a Bodyfit member. SIGN IN or JOIN TODAY!

Product Overview

Two Optimum Nutrition bottles standing next to each other.






High-Calorie WeighT GAiner

  • 1,250 Calories per Serving
  • 50 Grams of Protein per Serving
  • 250+ Grams of Carbohydrates per Serving
Optimum Nutrition Micronizec creatine power bottle

Optimum nutrition true strength

True Strength is a journey. It never rests, it never quits. It's about overcoming obstacles, accomplishing goals, and recognizing achievements. And then it resets to achieve again. As your trusted sports nutrition partner in goal achievement, ON demonstrates that same passion while crafting our products. From the raw materials we source to our state-of-the-art manufacturing processes, no compromises are made. You set the bar higher after every workout, we set the bar higher to redefine the industry standards and ensure you realize optimum results.


Packing a very substantial 1,250 calories into every serving – even more when mixed with cold milk – Serious Mass is the ultimate weight gain formula. With 50 grams of muscle building protein, when used in conjunction with a healthy, balanced diet and regular weight training, this powdered mix provides you with serious weight gaining support for developing your physique to the fullest.


Optimum Nutrition has been spotting the efforts of goal driven individuals since 1986. As one of the few companies to own and operate state-of-the-art manufacturing facilities that are GMP compliant and NSF Certified for Sport, ON assures that every shake will mix up effortlessly because the company started instantizing powdered products back in 2000. You also expect each shake to taste the same as the last and your next. That’s the kind of consistency ON delivers.

History & Heritage

Optimum Nutrition is legendary for both quality and innovation. In addition to producing the world’s best-selling whey protein, ON’s Gold Standard 100% Casein introduced slow-digesting nighttime protein to the weight training world and Amino Energy created the anytime energy category in sports nutrition. When technology makes advancements possible, ON will be the company bringing it to you.

serious mass ideal usage occasions

Ratings & Reviews

Serious Mass Weight Gainer
Overall Rating
1,154 Ratings
Verified Buyer Rating
452 Ratings
Average Flavor Rating
7 Flavors
Top Rated Flavor
Chocolate Peanut Butter
By clicking the button above, you agree to entering the Reviews section. Products in the Store are not intended to diagnose, treat, cure, or prevent any disease.
May 12, 2021
  • 8 Chocolate

Flavor tastes great, like hot chocolate. It mixes very easily in a blender but have to drink it in serving as it doesn’t fit in a 22oz shaker cup. Highly recommended to get in quick carbs and protein post workout or any time.

Apr 02, 2021
Verified Buyer
  • 10 Banana
Mar 02, 2021
  • 10 Chocolate

Great product! I felt I started gaining weight two days later after I started consuming. It can be easily digested but causes some bloating. I drank it before bed for weight gain. I gained 3 kg within a week, also The taste is very good.

Feb 11, 2021
  • 8 Chocolate

Hard to get the whole shake down, however using whole milk, bananas and sometimes peanut butter makes the taste better and adds cals. Tastes pretty good

Feb 05, 2021
  • 8 Chocolate

this product is a whole cheat code for bulking if anyone asks me for any tips on bulking this is what i tell them about!

Dec 26, 2020
Verified Buyer
  • 10 Chocolate Peanut Butter

This is the best mass gainer I have tried. Great blend-ability. Been using it roughly twice a day between meals and the results a obvious. Starting about 4 months ago I have now gained 10lbs and my goal of benching 225lbs x 20 has been surpassed to completing 21 rep sets now. I began at 13reps. Overall body size has increased dramatically.

May 29, 2020
  • 10 Chocolate Peanut Butter

I am using these product from last 2 weeks while its amazing product. I recommend to everyone use this product

May 28, 2020
Verified Buyer
  • 10 Chocolate
  • 5 Vanilla

The Vanilla flavor is a little chalky once it comes to texture however, other than that once blended with the right mixtures, it"s flame! The Chocolate flavor is enjoyable. You DO get Results from this product as well, after a solid use of 3 months accompanied by intense work outs.

Apr 24, 2020
  • 10 Chocolate

Flavour is great, tastes like chocolate milk. Scoops are large I did half servings morning and afterworkout/evening.

Apr 22, 2020
Verified Buyer
  • 8 Chocolate Peanut Butter

I started at 162LBS (6'2') and after taking this twice a day (1 scoop each time) I'm weighing 170LBS. about to order again and planning to eat more as well. Heres how I did it-- one scoop, 16 ounces of whole milk, a 3 scoops of ice cream, .. sometimes I would throw a banana or a tablespoon of peanut butter but that always made it hard to get down.

Apr 17, 2020
Verified Buyer
  • 10 Chocolate Peanut Butter

This is gonna help so much for me and I'm so glad I finally got mine! Just had a curious questions my nutritional facts are the one from Vanilla (I think) but I got chocolate Peanutbutter, but its no biggie, they aren't much different from nutritional facts, but taste is obviously different, im for sure going to buy another bag of this! Totally recommend for people who can't put on weight or trying to bulk up!

Apr 17, 2020
Verified Buyer
  • 10 Vanilla

Ive been taking this product about two months..1 serving after my workout with cell tech creatine fruitpunch at 8am and the second serving around lunch time and i must say I've gain around 12 to 15lbs easy...but you have to put the work in...working out..and all i do is push ups and this product is the real deal!!..and i eat my 3 regular meals a day..breakfast..lunch and if you want the gains..use this product and cell tech creatine fruitpunch WORKKKS!!!

Mar 27, 2020
Verified Buyer
  • 9 Vanilla

I use a scoop of this (625 cal, 25g of protein) and a scoop of syntha-6 vanilla protein. I blend it, and it comes out to 825 cal, 47g of protein after my afternoon workout. The flavor that comes out of this is awesome, tastes great and is filling as heck. Serious mass alone flavor is great too, I've put on roughly 13 pounds in 3 months, a lot of muscle but some fat included. It's just what happens unless you are tracking your exact macros/etc which I don't. Happy with this product

Mar 24, 2020
  • 9 Chocolate Peanut Butter

Really good mass gainer which helped me get 15 pounds of weight. I really like the chocolate peanut butter flavour. I took 2 scoops of mass gainer twice a day and beleive me it has seriously good results.

Mar 16, 2020
Verified Buyer
  • 8 Chocolate

Great weight gainer- helped me put on 10kgs in just a few months. Doesnt mix particularly well, so I'd recommend a blender if possible. Choc Mint flavour has some poor reviews but I really like it (although it kinda grew on me- the first time I didn't like it that much). I split the portions into 2, as 1200 calories in a single hit is quite a lot. I have half a serving twice a day and have definitely reaped the rewards (especially coming from someone who struggles like hell to put on any weight). 10/10 would recommend.

2 Sizes
12 Lbs.
Choose a Size
{{group.violatorText}} {{}}
5 Flavors
Chocolate Peanut Butter
Choose a Flavor
Flavor Rating: {{sku.flavorRating | flavorRating}}
Save 20% in Cart
Was:  {{}}
Price: $56.99  ($3.56 / Serving)
Flavor Rating: 8.9


Become a BodyFit Member

BodyFit Membership means up to 10% OFF EVERYTHING and FREE shipping.

Oh... and you also get:

• Access to exclusive workout plans and database

• Detailed exercise instructions

• Customized recommendations for all your fitness goals

Get free shipping and save an additional 10% on today's order

Loaded with 1,250 Calories, 50g of Protein, & 25 Vitamins and Minerals to Pack on Pounds*

What's in Optimum Nutrition Serious Mass Weight Gainer

12 Lbs. Chocolate Peanut Butter
Serving Size About 2 Heaping Scoops (336 g)
Servings Per Container16
Amount Per Serving In Water % Daily Value
Calories 1,250       
Total Fat 4 g 5%*
Saturated Fat 2.5 g 13%*
Cholesterol 95 mg 32%
Total Carbohydrate 253 g 92%*
Dietary Fiber 4 g 16%
Total Sugars 16 g **
Includes 10g Added Sugars 20%
Protein 50 g 100%*
Vitamin A (as beta-carotene) 940 mcg 104%
Vitamin C (as ascorbic acid) 60 mg 67%
Vitamin D (as cholecalciferol) 5 mcg 25%
Vitamin E (as d-alpha tocopherol succinate) 20 mg 133%
Thiamin (as thiamin mononitrate) 4.8 mg 400%
Riboflavin 4 mg 308%
Niacin (as niacinamide) 50.2 mg 314%
Vitamin B6 (as pyridoxine hydrochloride) 5 mg 294%
Folate (as folic acid) 680 mcg 170%
Vitamin B12 (as cyanocobalamin) 11 mcg 458%
Biotin (as d-biotin) 300 mcg 1,000%
Pantothenic Acid (as d-calcium pantothenate) 25 mg 500%
Choline (as choline bitartrate) 250 mg 45%
Calcium (as calcium citrate, dicalcium phosphate) 610 mg 47%
Iron (as ferrous fumarate) 9 mg 50%
Phosphorus (as dicalcium phosphate, dipotassium phosphate) 540 mg 43%
Iodine (as potassium iodide) 53 mcg 35%
Magnesium (as magnesium aspartate) 180 mg 43%
Zinc (as zinc citrate) 15 mg 136%
Selenium (as selenomethionine) 71 mcg 129%
Copper (as copper gluconate) 1 mg 111%
Manganese (as magnesium aspartate) 2.45 mg 107%
Chromium (as chromium polynicotinate) 120 mcg 343%
Molybdenum (as molybdenium amino acid chelate) 80 mcg 178%
Sodium 690 mg 30%
Potassium (as dipotassium phosphate) 1,110 mg 23%
Creatine Monohydrate 3 g **
L-Glutamine 500 mg **
Inositol 250 mg **
PABA (para-aminobenzoic acid) 5 mg **
* Percent Daily Values are based on a 2,000 calorie diet
** Daily Value not established
Other Ingredients:
Maltodextrin, Protein Blend (Whey Protein Concentrate, Calcium Caseinate, Egg Whites, Sweet Whey), Cocoa Powder (Processed with Alkali), Natural And Artificial Flavor, Medium Chain Triglycerides, Creamer (Sunflower Oil, Maltodextrin, Modified Food Starch, Dipotassium Phosphate, Tricalcium Phosphate, Tocopherols), Salt, Sucralose, Acesulfame Potassium.

Directions For Serious Mass Weight Gainer:

Add two heaping scoops of Serious Mass to a blender filled with 24 oz (710 mL) of  cold water, milk or other beverage. Blend for 30-45 seconds until dissolved.

TIPS: New users may find it beneficial to begin with 1/2 of a serving daily for the first week and then gradually increase to 1 serving a day.

Warnings: Store in a cool, dry place.

* These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Learn more about Whey Protein.
Check out other Performance Products.