Downward social comparisons to others in a relatively unsuccessful group can bolster mood, a phenomenon known as the big-fish-in-a-little-pond effect (BFLPE). The current study examined social support as a moderator of the BFLPE in online weight-management support groups (SGs). Participants (N = 149) were recruited from weight-management message boards. In an Internet survey, participants made weight-related social comparisons to the average person and the average SG member. Big fish indicated that they would feel more self-pride after reading a downward social comparison message than did other participants, but the BFLPE occurred only for participants with lower weight-related social support. Social support could foster collective identity in online self-help support groups, reducing the BFLPE.