<p>The present research examined the moderating effect of patient health engagement on the relationship between perceived stress and treatment adherence among patients with kidney failure undergoing hemodialysis. In this cross-sectional study, 184 patients from three hemodialysis outpatient clinics in Türkiye completed the Perceived Stress Scale, Patient Health Engagement Scale, and End-stage Renal Disease Adherence Questionnaire. Descriptive and inferential analyses preceded a moderation test using Hayes’ PROCESS macro (Model 1) with age and weekly dialysis frequency as covariates. Results supported H1, showing that higher perceived stress was associated with lower adherence (b =− 25.90, SE = 6.38, <i>p</i> &lt; 0.001), and in line with H2, the stress × engagement interaction was significant (b = 4.29, SE = 1.24, <i>p</i> = 0.001, ΔR² = 0.034), suggesting that engagement buffers the adverse impact of stress on adherence. Simple-slope analyses revealed that stress negatively predicted adherence at low (b = − 12.98, <i>p</i> = 0.001) and average engagement (b = − 7.09, <i>p</i> = 0.011), but not at high engagement (b = − 1.20, <i>p</i> = 0.697). These findings highlight patient health engagement as a protective resource that buffers stress-related non-adherence, suggesting that interventions to strengthen engagement may enhance adherence in hemodialysis care.</p>