This study was conducted to assess the effects of leadership styles and perception discrepancy (between followers and leaders) on leadership effectiveness to knowledge workers who require a relatively high degree of autonomy. We asked district prosecutors in Taiwan as our respondents and 489 valid samples were collected to test the proposed research model (20 questionnaires were from the chief district prosecutors and 469 questionnaires from district prosecutors). We hypothesized that transformational leadership is effective even when a high degree of autonomy is required by the followers. The research results highly support our hypotheses and demonstrate positive effects of both transformational and transactional leadership styles and negative effects of laissez-faire leadership on leadership effectiveness. The results also show a negative relationship between perception discrepancy and leadership effectiveness on knowledge workers. Managerial implications, research limitations and future research are discussed in the last section of the paper.