Approximately one-third of breast cancer survivors experiences persistent fatigue for months or years after successful treatment completion. There is a lack of evidence-based treatments for cancer-related fatigue, particularly among cancer survivors. This single-arm pilot study evaluated the feasibility and preliminary efficacy of a yoga intervention for fatigued breast cancer survivors based on the Iyengar tradition. Iyengar yoga prescribes specific poses for individuals with specific medical problems and conditions; this trial emphasized postures believed to be effective for reducing fatigue among breast cancer survivors, including inversions and backbends performed with the support of props. Twelve women were enrolled in the trial, and 11 completed the full 12-week course of treatment. There was a significant improvement in fatigue scores from pre- to post-intervention that was maintained at the 3-month post-intervention followup. Significant improvements were also observed in measures of physical function, depressed mood, and quality of life. These results support the acceptability of this intervention and suggest that it may have beneficial effects on persistent post-treatment fatigue. However, results require replication in a larger randomized controlled trial.