PURPOSE: To examine the effect of regular Iyengar yoga practice on measures of self-perceived psychosocial function and diurnal salivary cortisol secretion in stage II-IV breast cancer survivors (n = 18).DATA SOURCES: Women were randomly assigned to attend yoga practice for 90 min twice weekly for 8 weeks (n = 9) or to a wait-listed, noninterventional control group (n = 9). Traditional Iyengar yoga routines that progressively increased in difficulty as participants gained strength and flexibility were used. At baseline and after the 8-week study period, women completed self-report instruments to document various aspects of psychosocial and physical functioning, and collected salivary samples for cortisol analysis four times during the day for two consecutive days. CONCLUSIONS: The yoga group had lower morning and 5 p.m. salivary cortisol and improved emotional well-being and fatigue scores. IMPLICATIONS FOR PRACTICE: Breast cancer survivors are at risk for chronic psychosocial distress that may alter activity of the hypothalamic-pituitary-adrenal axis, resulting in aberrant regulation of cortisol secretion and increased risk of immune dysfunction and cancer progression. Regular yoga practice may be a low-risk, cost-effective way to improve psychosocial functioning, fatigue, and regulation of cortisol secretion in breast cancer survivors. These findings require validation with a larger randomized study.