BACKGROUND Because obesity is an independent risk factor for breast cancer recurrence, assessment of body composition is crucial to guide weight management in breast cancer survivors (BCS). This study assessed whether dual-energy x-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA) yield similar results for body composition in BCS. METHODS Body fat percentage, lean body mass, and fat mass were estimated using DXA and BIA under fasting conditions in 89 BCS. BMI categories included normal (18-24.99 kg/m2 ; n = 28), overweight (25.0-29.9 kg/m2 ; n = 21), obese (>30 kg/m2 ; n = 23), and severely obese BCS (>35 kg/m2 ; n = 17). Agreement between the devices was assessed by Bland-Altman analysis. RESULTS There was no agreement between the 2 devices for body fat percentage (DXA: 44.2 ± 6.2% vs BIA: 40.4 ± 7.8%), lean body mass (DXA: 39.1 ± 7.6 kg vs BIA: 42.9 ± 5.9 kg), and fat mass (DXA: 32.4 ± 10.8 kg vs BIA: 30.6 ± 11.0 kg; P < .001). These findings were consistent in normal, overweight, and obese BCS. There was agreement between the 2 devices for fat mass (DXA: 48.7 ± 7.2 kg vs BIA: 47.9 ± 5.7 kg) in severely obese BCS (P = .102), possibly due to small sample size. CONCLUSIONS BIA may underestimate body fat percentage and fat mass and overestimate lean body mass, compared with DXA. Future studies are warranted to assess the use of these 2 devices in a larger cohort of BCS within BMI categories.