Risk factors for lymphedema and related arm symptoms in breast cancer (BC) survivors have not been examined using a large prospective population-based cohort. The Iowa Women's Health Study (IWHS) collected self-reported data for diagnosed lymphedema in 2004, and data for cancer diagnosis, treatment, behavioral and health characteristics between 1986 and 2003. We studied 1,287 women, aged 55-69 at baseline, who developed unilateral BC: n = 104 (8%) with diagnosed lymphedema, n = 475 (37%) with arm symptoms but without diagnosed lymphedema, and n = 708 without lymphedema. Age- and multivariate-adjusted logistic regression models examined risk factors for lymphedema and related arm symptoms (OR [95% confidence interval]). The mean time between BC and the 2004 survey was 8.1 ± 5.0 (mean ± SD) years. After multivariate adjustment, the following cancer characteristics were positively associated with lymphedema: tumor stage (regional vs. in situ: 3.92 [1.61-9.54]), number of excised nodes (highest vs. lowest quintile: 3.52 [1.32-9.34], P (trend) = 0.003), tumor-positive nodes (yes vs. no 2.12 [1.19, 3.79]), and adjuvant chemotherapy (yes vs. no: 3.05 [1.75-5.30]). Several health characteristics were positively associated with lymphedema: baseline body mass index (highest vs. lowest tertile: 3.24 [1.70-6.21]), waist and hip circumference, and general health (fair/poor vs. excellent: 3.44 [1.30-9.06]). Positive associations with arm symptoms were number of excised nodes (highest vs. lowest quintile: 2.38 [1.41-4.03], P (trend) = 0.007), axillary radiation (yes vs. no: 1.72 [1.15-2.57]), and baseline general health (fair/poor vs. excellent: 4.27 [2.60-7.00]). In the IWHS, obesity, poorer general health, and markers of more advanced cancer were risk factors for lymphedema and related arm symptoms in BC survivors.