This paper uses a mobility biography approach to investigate how life course events explain changes in attitudes towards and levels of bicycling. We use 54 interviews conducted with residents of a small US city that include retrospective questions covering six life stages.Three life events emerged from the interviews as influential: parenthood, residential relocation, and meeting a new partner. Most participants with children related their level of bicycling and bicycling attitudes to their children. The impact of children on parental bicycling was non-linear over time, and varied throughout the child’s development and between couples or partners. Residential relocation affected attitudes towards and use of bicycles as well. The presence of bike infrastructure, supportive peers, and bicycling culture moderated this process. Meeting new partners prompted participants to discover new types of bicycling and contributed resources that facilitated or impeded bicycling. Our findings provide evidence for a bi-directional relationship between bicycling attitudes and behavior. As life events trigger changes in one of these two variables they are likely to change the other variable as well.The results point to four causal mechanisms that drive changes of bicycling attitudes and behavior in response to life events: Life events trigger a deliberation process, change social norms, unleash a latent demand for bicycling, and change interest in destinations and activities. These causal mechanisms may be generalizable to other transport modes as well. Life events may present a “windows of opportunity,” when persons are more susceptible to change, that planners could make use of to encourage behavior change.