Post-traumatic growth (PTG) is a positive psychological change experienced as a result of adversity, such as breast cancer (BC). Positive emotions are closely associated with PTG. Based on the broaden and build theory, positive emotions broaden cognition and behaviour to promote the generation of and reception to a wide range of ideas and actions. Accordingly, PTG could foster participation in health enhancing moderate-to-vigorous physical activity (MVPA) among breast cancer survivors (BCS) coping with cancer-related trauma, however this relationship is not well understood. This study examined the association between PTG and change in MVPA over the first year following BC treatment by testing the hypothesis that BCS who experience PTG adopt effective and healthy coping strategies, including MVPA, to deal with cancer-related trauma. Women (n = 178) wore an accelerometer at two time points one year apart and completed the PTG survey at baseline. Residual change scores were calculated for MVPA. Preliminary findings show a significant decrease in MVPA over time, t(177) = 2.31, p =. 02 and moderate PTG scores. The PTG subscales of new possibilities and appreciation for life were significantly (p < 0.05) correlated with change in MVPA (r = .19 & .15, respectively). Both dimensions were also significant (p < 0.05) predictors of change in MVPA (R2 = .08 & .09) after controlling for cancer and personal characteristics. Feelings of new possibilities and appreciation for life may encourage new skills and greater value for one's life and priorities, leading to greater participation in MVPA following BC treatment.