Objective Sedentary behavior is recognized as an independent risk factor for chronic diseases. Cancer survivors report high levels of sedentary behavior. In secondary analyses, we examined the effects of an exercise intervention on sedentary behavior (sitting time) among breast cancer survivors. Methods Seventy‐six breast cancer survivors (mean age = 55.62 y, mean 1.1 y since diagnosis) were randomized to receive either a 12‐week telephone‐delivered exercise intervention from peer volunteers or a contact control condition. The intervention did not specifically address sitting time. Participants' sedentary behavior was assessed for 7 days at baseline, 12 weeks, and 24 weeks via self‐report and objective measurement (accelerometer). Results At baseline, our sample reported sitting for 7.75 hours/day (10.98 h/d by accelerometer data). Spearman rank correlations showed significant positive correlations at baseline between sitting time measured by self‐report and accelerometer (ρ = 0.37; P = .002) in the entire sample. There were no significant changes over time within group nor were there any significant intervention effects on sitting time (self‐report and objective) at 12 and 24 weeks (all P's > .05). Conclusions An exercise intervention that did not focus specifically on sitting time did not affect sedentary behavior among breast cancer survivors. Intervention components that specifically target sitting behavior are needed to reduce this risk behavior among survivors.