This study investigated the impact of a building-resilience intervention on coping and posttraumatic growth (PTG) in a convenience sample of 94 breast cancer survivors. PTG was divided into constructive and illusory components, based on the two-sided Janus face model (Maercker & Zoellner, 2004). We operationalized constructive PTG as an improvement in both PTG and coping, and illusory PTG as an improvement in PTG only. An 8-session group intervention was delivered to 49 women (mean age = 51.5 years, SD = 10.7) who completed self-report questionnaires at baseline and at 6 months follow-up; a control group of 45 women only completed questionnaires. More than half the participants (n = 53; 56.38%) reported increased PTG at 6 months (mean change = 0.56, SD = 0.48, η(2) = .58). The increase in both PTG and positive coping was significantly greater in the intervention group than the control group (B = 0.23 for PTG, and B = 0.35 for positive coping). Further, a higher proportion of constructive PTG (vs. illusory PTG) was reported by the participants in the intervention group (89.3%), as compared to the control group (56.3%; z = 2.57). The distinction between constructive and illusory PTG has clinical implications for interventions promoting coping and growth among cancer survivors.