Adults with traumatic brain injury (TBI) often report reduced social participation and loss of friends, but little is known about quality of friendship after TBI. Our objective was to characterize social participation, friendship quantity, and friendship quality of adults with TBI and a comparison group of uninjured adults. Participants included 18 adults with moderate to severe TBI and 16 of their informant friends; and 18 uninjured adults and 11 of their informant friends. The main measures used were the Participation Assessment with Recombined Tools-Objective, the Social Network Questionnaire, and the McGill Friendship Questionnaire. Participants with TBI reported significantly less social participation and had fewer total friends, although this difference was not statistically significant. Adults with TBI differed from their friends on one measure of friendship quality, but reports for friendship quality were high in both groups. Adults with TBI reported overall high levels of friendship quality despite having lower levels of social participation compared with uninjured adults. Future research should investigate how the balance of quantity and quality of friendships relates to satisfaction with social participation and overall quality of life.