The study explored the school heads' internal quality assurance practices in public secondary schools of Panabo City Division. Also, it investigated the association of the involved variables of school heads' internal quality assurance practices. With the use of probability sampling, 156 public secondary teachers were selected as the respondents and ten (10) informants for the qualitative phase. Utilizing the sequential explanatory mixed methods approach, the data collated were analyzed through the use of Mean and ANOVA for quantitative phase and thematic analysis for qualitative phase. Results revealed that there was a high school heads' internal quality assurance practices among the respondents which was confirmed by the informants. Specifically, both quality teaching and learning and quality curriculum implementation were considered as high. Furthermore, the null hypothesis was accepted. Hence, there was no significant difference in the internal quality assurance practices of school heads when analyzed by school category. In the qualitative phase, the informants confirmed that quality teaching and learning and quality curriculum were evident in the school. Based on the findings, it was further suggested that higher officials in the Department of Education may identify means on how to strengthen the school heads' internal quality assurance practices. More so, future researchers may further explore the internal quality assurance practices of school heads considering other factors and research methods.