Abstract Objective To evaluate the association between adherence to the Dietary Approaches to Stop Hypertension (DASH) diet and overall and cause-specific mortality in the Golestan Cohort Study (GCS). Methods A total of 50 045 participants aged 40 years or older were recruited from Golestan Province, Iran, from 2004 to 2008 and followed for a mean of 10.64 years. The DASH diet score was calculated for each individual based on food groups. The primary outcome measure was death from any cause. Results During 517 326 person-years of follow-up, 6763 deaths were reported. After adjustment for potential confounders, DASH diet score was inversely associated with risk of death from all causes and cancers [hazard ratio (HR): 0.86; 95% confidence interval (CI): 0.75, 0.98; and HR: 0.65; 95% CI: 0.47, 0.90, respectively]. A higher DASH diet score was associated with lower risk of gastrointestinal cancer mortality in men (HR: 0.55; 95% CI: 0.30, 0.99). A greater adherence to DASH diet was also associated with lower other-cancer mortality in women (HR: 0.50; 95% CI: 0.24, 0.99). No association between DASH diet score and cardiovascular disease mortality was observed, except that those dying of cardiovascular disease were younger than 50 years of age and smokers. Conclusions Our findings suggest that maintaining a diet similar to the DASH diet is independently associated with reducing the risk of total death, cancers, and especially gastrointestinal cancers in men.