Background: Home-based parenting support within youth care services is one of the key interventions provided to families encountering difficulties with child rearing and child development. However, knowledge on factors contributing to positive outcomes of home-based parenting support is limited. Objective: The current study investigated the predictive value of (1) early parent-professional alliance and (2) change in alliance during care for outcomes of home-based parenting support. Method: Multi-informant self-report alliance and outcome data from 146 parents (Mage = 40.00, SD = 7.10; range 19-57 years) and their professionals collected early and late in care were analyzed using latent growth curve modeling. Results: Findings demonstrated that higher levels of early parent-reported alliance predicted higher levels of parent-reported satisfaction with care, and improved parent functioning. Higher levels of early professional-reported alliance predicted higher levels of parent- and professional-reported satisfaction, and improved parent functioning. Increases in professional-reported alliance during care predicted higher levels of professional-reported satisfaction and parent functioning but were not related to parent-reported outcomes. Change in parent-reported alliance was not related to outcomes. Conclusions: Together, our findings suggest that a strong parent-professional alliance represents a key process factor in realizing positive outcomes of home-based parenting support. Consequently, efforts in research and practice are needed to investigate precursors of strong alliances and to optimize professionals' ability to develop and maintain strong parent-professional alliances.