Introduction The prevalence of leisure-time physical activity has increased in recent decades, but values differ significantly among countries. Owing to the improvement of living standards, a higher frequency of leisure-time physical activity is expected in Western countries such as Spain, but there is a lack of research involving large, representative samples during a prolonged temporal frame to confirm this tendency. Methods Individual representative data from the 1987, 1993, 1995, 1997, 2001, 2011, and 2017 rounds of the Spanish National Health Survey were used. Statistical analyses were conducted from April 9, 2020 to May 5, 2020. Results A total of 114,813 participants (aged 43.9 [SD=16.7] years, 51.8% women) were included in the study. Crude linear trends in regular monthly and weekly leisure-time physical activity were estimated together using linear regression models across the survey years, which also served to estimate the regression coefficients (β) and 95% CIs for every year change. All age groups experienced significantly increased prevalence of regular leisure-time physical activity—either several times a month or several times a week—over time (p<0.001 for trend). Participants aged 16–17 years had the highest increase in the annual prevalence of regular leisure-time physical activity (β=0.8, 95% CI=0.7, 1.0). Additional adjusted multivariable logistic regression confirmed these trends. Conclusions This study shows an increase in regular leisure-time physical activity among the adult Spanish population during the period from 1987 to 2017. Younger participants consistently presented higher prevalence levels than older participants.