Retirement brings changes in daily life, which may have implications for life satisfaction and leisure-time physical activity (LTPA). This study sought to examine associations between concurrent changes in life satisfaction and LTPA across retirement, addressing gaps in understanding how life satisfaction influences physical activity in retirees. Study included 3535 public sector workers (83% women) from the Finnish Retirement and Aging study with annual surveys before and after retirement. Participants were categorized based on their Life Satisfaction Scale responses before and after retirement into Stable Low, Low-Increasing, Intermediate-Decreasing, Stable Intermediate, Intermediate-Increasing, High-Decreasing, and Stable High life satisfaction. Self-reported weekly LTPA during past 12 months was summarized as metabolic equivalent hours (METh/week). Generalized estimating equations were used to examine changes in LTPA across retirement transition among these groups, adjusting for sociodemographic and health-related factors. Compared to Stable Low, Low-Increasing life satisfaction was associated with increasing LTPA (mean difference 4.16 METh/week, 95%CI 0.85 to7.47). Compared to Stable Intermediate, Intermediate-Increasing life satisfaction was associated with increasing LTPA (mean difference 1.96 METh/week, 95%CI 0.03 to 3.88), while Intermediate-Decreasing life satisfaction was linked to decreasing LTPA (mean difference  −3 .79 METh/week, 95%CI −7.62 to 0.04). No differences were observed between Stable High and High-Decreasing life satisfaction. Changes in life satisfaction during retirement transition are associated with changes in LTPA, especially among those with low or intermediate life satisfaction before retirement. Further research is needed to assess, whether supporting life satisfaction in retirees could foster greater engagement in LTPA.