<p>This study, grounded in existential social work theory, investigates the relationship between specific free will beliefs (free will, scientific determinism, fatalistic determinism, and randomness) and authenticity among young adults in Türkiye. It further examines the mediating role of meaning in life, offering insights for clinical social work practice related to authenticity. The study employs structural equation modeling using data collected from 452 participants aged 18–45. Results show that free will belief positively predicts authenticity, while scientific determinism belief, fatalistic determinism belief, and randomness belief negatively predict it. Furthermore, the presence of meaning mediates the relationships between free will belief and authenticity (partially) and between randomness belief and authenticity (fully). The current study contributes to the limited empirical literature on the relationship between free will beliefs and authenticity, particularly from an existential social work perspective. It also highlights the significant role of life meaning in this relationship. These insights have important implications for clinical social work practice, suggesting that addressing free will beliefs and promoting meaning-making processes could be valuable tools in fostering authenticity and psychological well-being. These findings have significant implications for clinical social workers supporting marginalized communities in expressing their authentic selves and asserting their rights across diverse cultural contexts.</p>