This study examines the relationship between supervisor's budgetary style, supervisor's trust in subordinate and their effects on the subunit's performance of two newly privatised Malaysian utility companies. A framework linking uncertainty and organisational growth to subunit's performance is tested using structural equation modelling. In addition, the study examines the mediating role of trust in the relation between supervisor's budgetary style as a control system and subordinate's autonomy, which in turn could affect subunit's performance. Results confirm the hypothesised relationships. These findings contribute to understanding the role that trust plays in institutionalising a participative budgeting process during organisational change.