The social identity model of organizational leadership (SIMOL; Hogg and van Knippenberg, 2003 was extended analyzing the degree of employees’ effort as individual outcome of leadership effectiveness. Two studies were conducted with Italian participants. Study 1 was a survey conducted with 68 employees of a medium size company. Results showed the significant two-way interaction effect of team identification × leader group prototypicality in predicting employees’ work effort. Study 2, including 124 students, was a 2 × 2 within subject design (team identification high vs. low × leader group prototypicality high vs. low) using scenarios. Results confirmed experimentally the causal relationship between such variables: subjects in condition of high team identification and high leader group prototypicality perceive leaders as more effective than the subjects in the other three conditions.