Steering street-level bureaucrats is utterly complex due to their discretion and professional status which grant them relative autonomy from supervisory directives. Drawing from transformational leadership theory, this article explores the opportunities these work conditions provide for supervisory leadership at the frontlines. Looking at street-level bureaucrats’ attitude towards clients, we analyze how the frontline supervisor affects this core perception that protrudes the human judgments street-level bureaucrats are required to pass in their use of their discretion. Using a survey dataset of 971 street-level bureaucrats and their 203 frontline supervisors, this study shows that frontline supervisors function as an attitudinal role model to street-level bureaucrats. Moreover, their supportive leadership behaviors are crucial to them upholding a positive attitude towards clients. Supportive leadership does not unequivocally strengthen the supervisor’s position as an attitudinal referent, though. These findings challenge pessimistic assessments of the potential for supervisory leadership at the frontlines. Theoretical and practical implications are discussed.