The gender gap continues to exist in physics education. The author examines the gender-related differences in the relations and strengths among personal epistemologies, motivation, and achievement in physics among Turkish high school students. Established questionnaires were used to identify students' personal epistemologies, motivations and achievement in physics. A total of 567 ninth-grade students from three high schools in Mugla Province in Turkey participated in the study. Multigroup structural equation modeling was used to determine the gender differences in the relations and strengths among personal epistemology, motivation, and achievement in physics. Results from the structural equation modeling showed that students' personal epistemologies directly predicted their motivation and indirectly their achievement in physics. Multigroup structural equation modeling analysis showed that the strength of the relations between personal epistemology and motivation varied for female and male students. Implications for future directions are discussed.