In different theoretical traditions, negative social conditions, attachments, and interactions shape the way individuals view the law and its agents. Although most researchers acknowledge the conceptual distinction between different legal attitudes such as legal cynicism and police legitimacy, it remains unclear to what extent these attitudes stem from the same social sources. In the current study, therefore, we evaluate the social and individual factors that influence trajectories of legal cynicism and police legitimacy using a diverse community sample of youths in Zurich, Switzerland. Latent growth curve models were employed to examine patterns of change in legal cynicism and police legitimacy between 13 and 20 years of age. The findings show that legal cynicism and police legitimacy both decline into early adulthood and exhibit high rank‐stability over time. Furthermore, we find that legal cynicism is closely related to individual characteristics that reflect one's inability to recognize or abide by their internal rules. By contrast, police legitimacy is shaped by socialization influences, particularly teacher bonds and police contacts. These results indicate a need to assess the measurement and interpretation of legal cynicism critically in relation to broader legitimacy beliefs and to investigate the shared and distinct sources of these different constructs.