The study aims to investigate the effect of employees' participation in the budget construction process, through voice and trust, on employee self-efficacy and performance, in public sector organizations. Budgetary participation and employees' performance have been extensively researched in both private sector organizations and from the perspective of top management. We investigated the phenomenon in public sector organizations and from the point of view of lower level participating employees. We gleaned empirical data from 114 respondents in public sector organizations in Lampung, Indonesia, and analyzed it using SmartPLS to test our hypotheses. We found that in the course of budgetary participation, employees' expectancy attitude, in the light of the expectancy theory and Maslow's hierarchy of needs, predicted employees' behavior, and had a significant impact on their self-efficacy and performance. Employees' voice and interpersonal trust in the budget construction process would reap optimal benefit for the organization when participating employees perceive their participation to be objectively appreciated and encouraged by top management. The study has implications for top management's role in the budget construction process, and contributes to the management accounting literature in the context of the public sector in developing countries.