Watching sports at stadiums can have a favorable impact on health-related outcomes in older adults. We examined the effect of watching professional baseball at a ballpark on older adults' health-related outcomes.A total fo 58 participants aged 65-85 years were randomized into a spectator group (n = 29) and waiting-list group (n = 29). During the 2-month intervention, there were 21 games. The spectator group watched games at the ballpark, and the waiting-list group maintained their daily routines. The health-related outcomes were executive and cognitive functions, health-related quality of life, depression symptoms, subjective happiness and physical activity.The median days watching baseball games in the spectator group was 6 days (interquartile range 4-10 days). Executive function using the reverse Stroop interference rate showed a non-significant trend of improvement in the spectator group compared with the waiting-list group (P = 0.063). The spectator group showed a significant reduction in depressive symptoms compared with the waiting-list group (P = 0.016).Regularly watching professional baseball at a ballpark reduced older adults' depression symptoms. Geriatr Gerontol Int 2019; 19: 717-722.