A strong parent-professional alliance that increases over the course of care predicts positive outcomes of home-based parenting support. However, little is known about factors that influence the development or maintenance of the alliance in home-based parenting support, limiting professionals' ability to optimize the parent-professional alliance and thereby the quality of care. Therefore, the present study examined whether voluntary versus mandated service involvement, previous involvement in similar services, parenting stress, child psychosocial problems, and care expectations were associated with early parent-professional alliance and predicted change in alliance during home-based parenting support services. Questionnaire data from 60 parents (M age = 40.65 years, SD = 6.81, range 23–55 years) and their professionals collected early and late in care were analyzed using structural equation modeling. Results indicated that previous involvement in similar services was related to lower levels of early parent-reported alliance, whereas positive care expectations were related to stronger early parent- and professional-reported alliances. Moreover, care expectations predicted change in professional-reported alliance during care, with positive parent expectations predicting a decrease and positive professional expectations predicting an increase in alliance. Voluntary versus mandated service involvement, parenting stress and child psychosocial problems were not found to influence the alliance. These findings emphasize the need for professionals to discuss previous service involvement and care expectations as well as a need for future studies to identify other factors that influence alliance and alliance-building skills.