To build on the growing literature on interpersonal relationships among individuals with PTSD, this study examined the separate influences of PTSD symptoms and depression on functioning with friends, romantic partners, and family. To examine the influence of measurement, both interviewer-rated assessment of interpersonal functioning and self-reported assessment of perceived social support were included. The sample included 109 community members who sought help for mental health problems in the aftermath of a serious motor vehicle accident. Building on previous research, hierarchical regression models were used to examine the impact of re-experiencing, avoidance, emotional numbing, and hyperarousal on relationship functioning, followed by depression. Results suggest that assessment modality makes a difference in understanding factors contributing to interpersonal strain. When assessed by an interviewer, depression seems to play a larger role in interpersonal strain, relative to PTSD symptoms. When assessed via self-reported perceived social support, weaker associations were observed, which highlighted the role of emotional numbing. Results are discussed in light of the possible role that PTSD comorbidity with depression plays in interpersonal functioning following a traumatic event, with implications for future research.