This study explored the effects of explicit and implicit epistemologically enhanced instructions probing 9th-grade students' personal epistemologies on their physics-related personal epistemology (PPE) and physics achievement in the heat and temperature unit. In the implicit epistemologically enhanced instruction (IEEI), different dimensions of personal epistemologies were implicitly embedded into the instructional design without an explicit reference to personal epistemologies. On the other hand, in explicitly enhanced epistemological instruction (EEEI), the same instructional design was used with an explicit reference to personal epistemologies through discussions, students' reflections, and teacher talks. A conventional instruction (CI), which included neither implicit nor explicit reference to personal epistemologies, was also used as a control group. A quasi-experimental research design was adopted to explore the effects of IEEI and EEEI on the students' physics-related personal epistemology and physics achievement, with 186 ninth graders participating in the study. Multivariate analysis of covariance (MANCOVA) was used to determine the differences between the groups exposed to three different instructional methods. The results showed that EEEI was the most effective method of instruction in improving students' physics-related personal epistemologies and achievement. The findings indicated that implicit/explicit epistemological enhancement strengthens the achievement in physics.