This mixed methods research investigated how young adult alumnae from a Catholic female high school perceive the impact of their high school service experience concerning their "beliefs" about the importance of service, current "engagement" in service, and their beliefs about and engagement with four Catholic Social Teaching principles (life and dignity, care for the poor, solidarity and common good, and rights and responsibilities) related to social justice. This research draws data from young adult alumnae from a Catholic female single-sex high school in a metropolitan city of the United States. The data collection included a web-based survey (N=131), individual interview (n=9), and school documents review. Catholic theology of the human person, and Catholic social teaching principles served as the conceptual framework for data analysis. This research draws data from young adult alumnae from a Catholic female single-sex high school in a metropolitan city of the United States. The data collection included a web-based survey (N=131), individual interview (n=9), and school documents review. Catholic theology of the human person, and Catholic social teaching principles served as the conceptual framework for data analysis. The quantitative data revealed that Catholic high school service program experience positively impacts participants' "beliefs" about the importance of service (65%), and the importance of four Catholic social teaching principles (73%). The qualitative data corroborates with the quantitative findings. However, participants lacked translating their beliefs in to action with only 42% reporting as "engaged" in service. Although a majority of participants (60%) reported as engaged in activities related to four CST principles, in reality only 25% are significantly engaged in service in the past 12 months. Catholic educators are invited to examine their service pedagogy and address factors that contribute to low level of service engagement. Further research is suggested to identify factors that would raise the level of service engagement in alumnae’s young adult life.