The aim of this study was to investigate the effect of nutrition and sexual health education on healthy lifestyle behaviours of teacher candidates (HLSB). In the research, a quasi-experimental research one-group pretest-posttest design, a quantitative research method, was used. The sample of the study consisted of 60 pre-service teachers studying at the science education department of a public university. The data were gathered by Healthy Lifestyle Behaviours (HLSB) Scale-II. It was determined that the levels of healthy lifestyle behaviours of the participants in both groups were low and close to each other before intervention. According to the results of nutrition education obtained from the research, there was found a significant difference in the average scores of the HLSB scale for the intervention group. They differed significantly by subscales and the overall score of HLSB except for the "Interpersonal Relations" subscale. The effect of given nutrition education on students' healthy lifestyle behavior levels was found to be 'very high'. According to the results related to sexual health education, healthy lifestyle behavior levels only differed in "Health Responsibility" subscale. In the study, no significant difference was found between the post-test scores of the students in both the nutrition and sexual health education groups. This result is interpreted that nutrition education and sexual education are similarly effective in students' healthy lifestyle behaviors. This result shows that "health education" should be reconsidered in accordance with today's health understanding defined as biopsychosocial. In order for students to develop healthy lifestyle behaviors, both nutrition education and sexual health education should be given.