This study aimed to investigate the mediating role of academic enthusiasm in the relationship between problem-solving skills and academic achievement, as well as to identify the factors influencing academic enthusiasm among upper secondary school students, employing a mixed-methods research design with a sequential explanatory approach. In this applied, descriptive-analytical study, the findings from both the quantitative and qualitative phases were integrated to provide a more comprehensive picture of the relationships among the research variables and their underlying determinants. The statistical population comprised all upper secondary school students in Minab County, totalling 4,406 individuals. Based on Krejcie and Morgan's table, a sample of 351 students was selected through stratified random sampling for the quantitative phase, while 16 participants were purposively selected for the qualitative phase, continuing until data saturation was achieved. Data collection instruments in the quantitative phase consisted of three standardized questionnaires: Hepner and Petersen's Problem-Solving Skills, Pham and Taylor's Academic Achievement, and Gunuc and Kuzu's Academic Enthusiasm Questionnaires. In the qualitative phase, semi-structured interviews were utilized. For data analysis, structural equation modeling using partial least squares (PLS) was employed for the quantitative phase, while thematic analysis was applied to the qualitative data. The results indicated that academic enthusiasm played a significant partial mediating role in the relationship between problem-solving skills and academic achievement (β = 0.450, P< 0.05, t>1.96). Furthermore, the qualitative findings revealed seven categories of influential factors pertaining to academic enthusiasm: (1) school-related factors, (2) individual psychological factors, (3) the role of educational technology, (4) the role of the community outside school, (5) the role of metacognitive strategies, (6) the role of economic factors, and (7) the role of physical health, all of which were identified as effective in this process. Given the mediating role of academic enthusiasm, it is recommended that teachers and educational counselors focus on enhancing these influential factors to facilitate the improvement of students' academic achievement.