Reflective supervision has been richly described within the literature, but has had little empirical, and particularly quantitative, examination. This longitudinal study used mixed methods to examine how early childhood teacher attachment and trauma histories may contribute to their stress in teacher-parent relationships, and how reflective supervision may impact this stress. Thirty-seven teachers (36 females, 1 male) were recruited from 5 early childhood sites that participated in reflective supervision: 18 were in their first year and 19 had participated in 2-5 years of reflective supervision. 73% of participants were Latino/a, and 29% held a bachelor's degree. Participants rated their own parental relationships during childhood, trauma history, and current compassion satisfaction, burnout, secondary traumatic stress, and frustration in a challenging teacher-parent relationship. A subsample of 20 teachers completed a qualitative interview, and among those, 14 teachers completed both pre- and post-assessments and the interview. The results provide evidence that a teacher's childhood parental relationships relate to their current frustration in teacher-parent relationships. Furthermore, findings suggest that more time spent in reflective supervision may help protect a teacher against some of these stressors. Relating these findings to the attachment literature, reflective supervision may offer a corrective experience for teachers similar to therapy or long-term adult relationships which impact attachment styles as they relate to work interactions. Implications and future directions are considered.