Purpose: Various aspects of diet have been implicated to play a role in the etiology of bladder cancer. Studies examining this association have been conducted primarily in Western countries but none in Middle Eastern Countries. Method: We examined the association between the dietary inflammatory index (DII®) and bladder cancer in an Iranian case-control study. A total of 56 incident cases with a mean age of 60 years and 109 controls with a mean age of 57 years, attending the same hospital as the cases during the same time period, were recruited. The DII is a literature-derived index developed to determine the inflammatory potential of diet and was computed using a validated food frequency questionnaire. Logistic regression was used to estimate odds ratios, with DII fit as continuous and as a dichotomous variable. Results: Multivariate analyses revealed that subjects with higher DII score (>-0.12) are at higher risk of bladder cancer [odds ratio (OR) = 2.46; 95% CI = 1.12-5.41, P value = 0.02)] compared to subjects with lower DII scores (≤-0.12). Stratified results showed stronger association was among current/ex-smokers (ORDII (>-0.12/≤-0.12) = 3.30; 95% CI = 1.07-10.16). Conclusion: These data suggest a pro-inflammatory diet may be a risk factor for bladder cancer among Iranians.