This prospective cohort study aimed to examine the associations of trust towards the supervisor (vertical trust) and trust towards co-workers (horizontal trust) with retirement intentions. The participants were 14 840 women and men working in the municipal sector in 2000–12 (Finnish Public Sector Study). Trust (vertical trust towards the supervisor and horizontal trust towards co-workers) and retirement intentions were assessed in repeated surveys. Multivariable multinomial logistic regression analyses were conducted to assess the association between baseline trust and retirement intentions at 3.7 years of follow-up. Demographic characteristics, health, psychological distress, health risk behaviors, personality factors, and psychosocial factors were included as covariates. Of the participants, 67.0% trusted their supervisor and 54.9% trusted their co-workers. Employees who trusted their supervisor (odds ratio (OR) 0.60, 95% confidence interval (CI) 0.53–0.67) and employees who trusted their co-workers (odds ratio 0.62, 95% confidence interval 0.55–0.70) at baseline were less likely to have strong retirement intentions at follow-up compared to those who did not trust. These associations largely persisted after adjusting for all covariates and taking into account baseline retirement intentions. In conclusion, trust in the supervisor and co-workers predicted retirement intentions. These observational findings suggest that increasing trust in the workplace may contribute to lengthening working careers and preventing early retirement.