Objective: Moderate-to-vigorous physical activity (MVPA) improves cardiovascular health. Few studies have examined MVPA timing. We examined the associations of timing of bout-related MVPA with cardiorespiratory fitness and cardiovascular risk in adults with type 2 diabetes. Methods: Baseline 7-day hip-worn accelerometry data from Look AHEAD participants (n=2,153, 57% women) were analyzed to identify bout-related MVPA (≥3 metabolic equivalent tasks (MET)/min for ≥10mins). Cardiorespiratory fitness was assessed by maximal graded exercise test. Participants were categorized into six groups based on the time of day with the majority of bout-related MVPA (MET×min): ≥50% of bout-related MVPA during the same time window (Morning, Midday, Afternoon, or Evening), Results: Cardiorespiratory fitness was highly associated with timing of bout-related MVPA (P=0.0005), independent of weekly bout-related MVPA volume and intensity. Importantly, this association varied by sex (P=0.02). In men, the midday group had the lowest fitness (β -0.46 [95%CI -0.87, -0.06]), while the mixed group in women was the least fit. Framingham risk score (FRS) was associated with timing of bout-related MVPA (P=0.02), which also differed by sex (P=0.0007). The male morning group had highest 4-year FRS (2.18% [0.70%, 3.65%]), but no association was observed in women. Conclusions: Timing of bout-related MVPA is associated with cardiorespiratory fitness and cardiovascular risk in men with type 2 diabetes, independent of bout-related MVPA volume and intensity. Prospective studies are needed to determine the impacts of MVPA timing on cardiovascular health.