Background <p>Biological Age Acceleration (BAA), as quantified by epigenetic clocks, is a well-established biomarker for mortality and age-related morbidity. This study aimed to investigate the independent and combined associations of sleep duration, sedentary behavior, and physical activity with BAA risk.</p> Methods <p>Leveraging the UK Biobank cohort, we conducted multiple linear regression analyses to assess the relationships between modifiable lifestyle factors and BAA. Nonlinear associations were evaluated using restricted cubic spline models, while causal inference was reinforced through two-sample Mendelian randomization analyses.</p> Results <p>A total of 241,125 participants (mean [SD] age, 55.99 [8.11] years; 124,029 female) were included in this analysis. Distinct non-linear patterns were discernible in the relationship of sedentary behavior, sleep duration, and physical activity with BAA risk. Sleep duration was correlated with BAA in a U-shaped pattern, with an apex of benefit at 7&#xa0;h nightly. Leisure-time physical activity related to BAA in an L-shaped curve, suggesting limited benefits beyond a threshold of activity. Conversely, sedentary behavior exhibited a linear relationship with BAA, characterized by a progressively escalating risk. Interaction analyses revealed that a combination of 7&#xa0;h of sleep, moderate-to-high leisure-time physical activity, and minimal sedentary behavior offered substantial protection against BAA (β = -0.775; 95% Confidence Interval, -0.849 to -0.702). These findings were substantiated by subsequent Mendelian randomization analysis.</p> Conclusions <p>Our findings demonstrate that modifiable lifestyle patterns—specifically increased leisure-time physical activity, optimized sleep duration, and reduced sedentary behavior—are significantly associated with attenuated biological aging. These results suggest behavioral modifications may represent viable strategies for decelerating aging.</p>