The retirement transition is a major life change affecting people’s lifestyles and behaviors, including those in relation to physical activity (PA), which is a key component of active ageing. Previous research analyzing the effect of retirement on PA levels has shown mixed results, and few studies investigated this issue in a gender perspective, thus, highlighting a need of knowledge in this respect. Aims of this study focused on the experience of PA during the retirement transition were to understand typologies of PA and possible changes in these typologies, to identify behavioural types relative to PA practice and levels, and to distinguish the main drivers and barriers for practicing PA associated with the different behavioural types. A further goal of the study was to investigate the abovementioned aims considering differences between women and men. Analyses were carried out within a three-year qualitative longitudinal study (2014-2016), which explored the individual experience of PA during the transition from work to retirement of 24 women and 16 men in Italy, with interviews carried out one year before and one and two years after retirement. Results show that preferred PA for both women and men was walking, along the transition to retirement. Over time, several participants replaced physically demanding activities with lighter ones. Six behavioural types were identified, describing individuals who incremented, started, or maintained the same level of PA, people who decreased PA levels or stopped it, and individuals who had a fluctuant behavior towards PA, or who had never practiced it. In general, poor health represented the main barrier to PA. For men, the main driver to PA was its effects on body shape, while for women, socialization/networking. In order to stimulate a more effective promotion of PA during the retirement transition, policy implications were discussed in light of the results obtained.