The literature of public service motivation (PSM) covers a variety of antecedents, but the discussion of trust, job selection, and line-staff is scant. The current study investigates how these factors influence Taiwan public managers’ PSM. Regression results show that manages working in organizations where the core function is supporting other agencies reported the lowest level of PSM. Managers selecting their current job based on the intrinsic need, extrinsic need, and amotivational need reported a high, middle, and low level of PSM respectively. The impacts of five types of trust on PSM differed between central government managers and local government managers, although in general trust was positively associated with PSM. Surprisingly, distrust in citizens was positively related to PSM for local level managers. Findings in the current study open a new window for PSM research regarding its interface with trust as a core component of social capital, line-staff functional difference as a classic public administration issues, and work needs as motivational styles.