The aim of the present study was to investigate the effect of personality traits pessimism and optimism on depression, anxiety and stress in breast cancer surgical patients. The sample included 58 women in the age range of 40-60 years (M = 57.80, SD = 11.95) scheduled for breast cancer surgery. Interrupted Time Series Design was used. The sample was selected through the Convenience Sampling Technique. The sample was included if they had not other serious diseases such as hepatitis, diabetes, cardiovascular or were not taking any antidepressants. The Life Orientation Test-R (Scheier, & Carver, 1985) was used to measure traits pessimism and optimism, which was translated in Urdu by the author. The Depression, Anxiety and Stress Scale (Talat, 2011) was administered to measure depression, anxiety and stress in these participants at pre-surgery, week 2nd and 6th weeks post-surgery. Results reveal that breast cancer surgical patients having pessimism experience significantly higher levels of depression, anxiety and stress at pre and at 2 points in time (i-e, 2nd & 6th week) post-surgery than optimistic women (P < .005). The data support hypotheses. The findings of study have practical implications in providing insight relevant for development and/or modifying trait optimism to overcome psychological distress in breast cancer surgical patients.