The aim of the study was to evaluate the impact of the state-wide dissemination of a physical activity (PA) intervention in Flanders. In 2011, a random sample was taken of the entire adult (25–75 years) population of Flanders. Data of the Flemish sample were compared with baseline data of the intervention and control group of ‘10 000 Steps Ghent’ (2005). In total, data of the International Physical Activity Questionnaire were available of 2556 respondents (1675 of the comparison sample and 881 of the Flemish sample). Pedometer data were obtained by 269 respondents of the Flemish sample and by 1236 respondents of the comparison sample. Compared with the comparison sample of 2005, the Flemish sample reported more walking ( P < 0.001), moderate ( P < 0.001), vigorous ( P < 0.001), work-related ( P < 0.001), leisure time ( P = 0.01) and household PA ( P = 0.03). Step count analyses revealed that the Flemish sample took more pedometer-based daily step counts ( P < 0.001) than the comparison sample. Furthermore, a higher proportion of respondents reaching the 10 000 steps/day goal ( P = 0.005) was found in the Flemish sample. A positive effect of ‘10 000 Steps Flanders’ was found. Results indicate that a state-wide approach based on socio-ecological models is an effective strategy to promote PA in a large population.