Seventy-five percent of epidemiological studies have reported that sedentary behavior is associated with ovarian cancer incidence. Although Japan has one of the most sedentary populations, with median sitting times of 7 h/day, this association has not been investigated. This study aimed to elucidate the association between average daily television (TV) viewing time, which is a major sedentary behavior, and the incidence of ovarian cancer in a large-scale nationwide cohort study in Japan.