Introduction: Phase angle (PA), a parameter that is obtained from body composition analysis, is an indicator of cellular health status. A lower PA in cancer patients can lead to a decrease in functional status and quality of life (QoL) and increased mortality. Studies have shown that physical activity increases PA. In this study, we aimed to examine the effects of Hatha yoga on PA, body composition, and QoL in patients with breast cancer. Methods: Thirty-one patients were randomized into the yoga (group 1, n = 15) and the control group (group 2, n = 16). Hatha yoga was practiced twice a week for 10 weeks in the intervention group. The PA of the patients was assessed using a body analysis instrument, and QoL was evaluated with an EORTC QLQ questionnaire both before treatment and at week 10. Results: Group 1 had significant improvements in the posttreatment EORTC QLQ functional and global scores (p < 0.05). In group 2, a significant improvement was observed in the EORTC QLQ symptom subscale (p = 0.035). PA values did not show any improvements in both groups (p > 0.05). Comparison of the 2 groups revealed no differences. Conclusion: Yoga may have beneficial effects on QoL in patients with breast cancer but does not have a significant effect on PA. There is a need for further studies to make a definitive statement.