The Relationships in Community Groups Trust Scale (RCG-TS) is an 11-item questionnaire to assess particularized trust in 3 groups: community- and congregation-based groups and families. It was developed using a multimethod approach employing in-depth interviews and qualitative analysis, followed by quantitative psychometric evaluation for construct, convergent, and concurrent validity and internal reliability. Means were compared between groups. In-depth interviews, expert review panel, and cognitive interviews contributed to content validity. Construct validity was supported through exploratory factor analysis indicating a single factor. The RCG-TS was significantly and positively associated with a sense of belonging scale in all three groups, supporting convergent validity. The RCG-TS trust scale was weakly correlated with the Lubben Social Network Scale, indicating concurrent validity. Internal consistency was high. These results suggest that the trust scale has sufficient reliability and validity for use in future research investigating trust in families and community groups within and outside congregations.