Breast cancer-related arm lymphedema is a serious complication that can adversely affect quality of life. Identifying risk factors that contribute to the development of lymphedema is vital for identifying avenues for prevention. The aim of this study was to examine the association between the development of arm lymphedema and both treatment and personal (e.g., obesity) risk factors. Women diagnosed with breast cancer in Iowa during 2004 and followed through 2010, who met eligibility criteria, were asked to complete a short computer assisted telephone interview about chronic conditions, arm activities, demographics, and lymphedema status. Lymphedema was characterized by a reported physician-diagnosis, a difference between arms in the circumference (> 2cm), or the presence of multiple self-reported arm symptoms (at least two of five major arm symptoms, and at least four total arm symptoms). Relative risks (RR) were estimated using logistic regression. Arm lymphedema was identified in 102 of 522 participants (19.5%). Participants treated by both axillary dissection and radiation therapy were more likely to have arm lymphedema than treated by either alone. Women with advanced cancer stage, positive nodes, and larger tumors along with a body mass index > 40 were also more likely to develop lymphedema. Arm activity level was not associated with lymphedema. Surgical methods, cancer characteristics and obesity were found to contribute to the development of arm lymphedema. Vigorous arm activity post-surgery was not found to increase the risk of arm lymphedema.