This research aimed to develop the children's trust in general social workers (CTGSW) scale. Psychometric properties, structural validity, construct, and concurrent validity of the scale were evaluated. Both linear and quadratic patterns between children's trust beliefs in social workers and their engagement with social workers were examined. A sample of 112 Italian vulnerable children (M = 11.4 years, SD = 1 month) were administered the Italian‐Children's Generalized Trust Beliefs scale, the CTGSW scale, and a measure of engagement with social workers. The CTGSW scale demonstrated the expected (a) structure validity; (b) acceptable psychometric properties; (c) construct validity by correlations with trust in significant others; and (d) concurrent validity by associations with children's engagement with social workers. Reliability and honesty bases of trust in social workers were associated with engagement with social workers. In comparison to the middle range, children who held very low trust in social workers demonstrated very low quality of relation with social workers. The pattern was asymmetrical. Children who held high trust beliefs in social workers demonstrated a modest decrease in quality of relation with social workers. The findings demonstrated validity and utility of the CTGSW and yielded support for the basis, domain, and target framework.