This is a randomized controlled experimental, sequential explanatory mixed-methods study that evaluated the effectiveness of an early childhood mental health professional development program, Caring with Caring, that was offered to early childhood educators working with infants and toddlers in a licensed group early childhood care and education program. I analyzed the characteristics of the participants and used quantitative measures to examine changes in their mindsets (e.g., belief/attitude, intention, identity) that might influence their caregiving behaviours. I conducted semi-structured interviews to disclose the participants' experiences in their own words and employed a meta-inference to portray a more accurate picture of the changes in the participants' mindsets through joint-display. The quantitative analysis revealed that there was a significant interaction between the participant groups and the two points in time, demonstrating statistical significance and a large effect, F (1, 27) = 13.60, p = 0.001, [eta]p[superscript 2] = 0.34, which was validated and supported by qualitative interview results. The results indicated promising improvement related to the three caregiving approaches (i.e., relationship-based, individualized, family-centred) as a result of participating in the professional development program. Those in the intervention group displayed increased confidence, felt better able to create a safe community, developed a better understanding of the British Columbia Early Learning Framework (BCELF), and expressed satisfaction with the professional development program. The findings of this study provide helpful insights for professional development program developers and providers, policymakers, managers of child care programs, and early childhood educators in promoting the mental health of young children in group early childhood care and education settings. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]