Summary Background Mortality benefits of vigorous leisure time physical activity (LTPA) among adults with NAFLD is not known. Aim To investigate association between LTPA and reduction in all‐cause mortality among adults with NAFLD. Methods We used NHANES (1999–2006) self‐reported PA data for adults (≥40 years) with mortality follow‐up through December 31, 2015. US‐Fatty Liver Index in absence of secondary causes identified NAFLD. Moderate and vigorous LTPA were calculated by the 2018 PA Guidelines for Americans. Results NAFLD prevalence among 5211 adults (46.2% male; 75.8% white; mean age 53.2 years) was 32.7%. Adults with NAFLD were less likely to report the recommended minimal PA (≥ 150 min/week, 55.5% vs 64.8%) or highly active PA (≥300 min/week, 39.2% vs 48.5%) compared to adults without NAFLD. Over a median follow‐up of 12.3 years, 355 deaths among adults with NAFLD and 510 deaths among adults without NAFLD were registered. In the metabolic comorbidities‐adjusted model, adults with NAFLD who reported ≥50% of their total PA as vigorous activity had a 56% reduction in all‐cause mortality risk (HR:0.44, 95%CI: 0.25–0.76) and cancer‐specific mortality risk (HR: 0.21, 0.06–0.66) but not cardiac‐specific mortality ( p > 0.05) compared to adults with NAFLD who did not report any LTPA. This association remained significant even among adults with NAFLD who met the recommended minimal PA, among adults with NAFLD who reported any LTPA, and among adults with NAFLD who had metabolic abnormalities and in sensitivity analysis. Conclusions Engaging in vigorous activity is beneficial for adults with NAFLD ‐ especially those with metabolic abnormalities.