The potential role of nutritional factors in multiple sclerosis (MS) etiology is not clearly understood. The authors investigated the association between dietary intake during adolescence with MS. This was a population-based incident case-control study in Iran with 547 incident cases and 1057 general population controls (7/8/2013-17/2/2015). Logistic regression was used to test differences in dietary intake between cases and controls adjusted for confounders. We found that a higher dietary consumption during adolescence of fresh fish, canned tuna, poultry, cheese, yogurt, butter, fruit, vegetables and a number of dietary supplements were associated with a significantly reduced risk of MS, while red meat, shrimp, and margarine were not associated with MS. Fresh fish had a dose-response association of 0.71 (0.58-0.88) per category increase, and consuming >0.5 serves of canned tuna fish per week had an OR of 0.72 (0.56-0.90); fruit intake had an OR of 0.82 (0.71-0.94) per category increase and cheese consumption an OR of 0.78 (0.67-0.91) per category increase. We identified that a higher intake of a number of food groups generally viewed as healthy were associated with a reduced risk of MS. A healthier diet during adolescence may be protective of developing MS.