Breast cancer survivors have reported dissatisfaction regarding their education on risk of breast cancer-related lymphedema (BCRL) from clinicians. We describe clinician knowledge and treatment referral of patients with BCRL among active oncologists, surgeons, and primary care physicians in the Kaiser Permanente Northern California Medical Care Program. A total of 887 oncologists, surgeons, and primary care clinicians completed a 10-minute web survey from May 2, 2010 to December 31, 2010 on BCRL knowledge, education, and referral patterns. A knowledge score of BCRL was calculated based on clinician responses. Multivariable regression models were used to determine the associations of selected covariates with BCRL knowledge score and clinician referral, respectively. Compared with primary care clinicians, oncologists had the highest mean score followed closely by surgeons (P < 0.0001). In multivariable analyses, being female, an oncologist or surgeon, and recently receiving BCRL materials were each significantly associated with higher BCRL knowledge scores. About 44% of clinicians (n = 381) indicated they had ever made a BCRL referral (100% oncologists, 79% surgeons, and 36% primary care clinicians). Clinicians with a higher knowledge score were more likely to make referrals. In stratified analyses by specialty, the significant associated factors remained for primary care but became non-significant for oncology and surgery. These results can inform educational interventions to strengthen clinician knowledge of the clinical management of BCRL, especially among primary care clinicians. With the growing number of breast cancer survivors, increasing clinician education about BCRL across all specialties is warranted.