Breast cancer (BC) survivors commonly face stressors that impact quality of life (Hadd et al., 2010). Social support facilitates coping, and is associated with positive adaptation and well-being (Nausheen et al., 2009; McDonough et al., 2014). Group physical activity programs such as dragon boating provide opportunities to obtain social support from other survivors (McDonough et al., 2011). However, little is known about how social support changes among survivors who join such programs, or about demographic, disease-related, and psychosocial predictors of change in social support. This study examined change in support for BC-related concerns over the first season of participation in a dragon boating program for BC survivors, and whether demographic, disease-related, and psychosocial factors predicted change over time. 22 women (Mage = 52.05 years, 86% Caucasian, Mtime since diagnosis = 1.60 years) were surveyed monthly during their first 8-months of participation. Multilevel modeling was used to examine change over time, and between-person predictors of change. There was an average linear increase in social support. Greater increases in social support were experienced by those with lower income (γ = -.06) and greater BMI (γ = .01); and by those who had completed treatment more recently (γ = -.02), had not participated in a BC support group (γ = -.08), and had experienced a cancer recurrence (γ = .29). Furthermore, greater increases in social support were experienced by those who had lower satisfaction of relatedness needs (γ = -.12), poorer physical self-worth (γ = -.04), and less social support for BC outside of the program (γ = -.11). Participating in group physical activity programs such as dragon boating is associated with increased social support for coping with BC, and women who may be most at risk to struggle in the wake of BC tend to experience the greatest gains in support.