Longitudinal research on students' interest in higher education showed that interest declines throughout the study program. While researchers reported numerous factors explaining interest on the student level, research on the relationship between the lecturer level and students' interest development is considered scarce. This study aimed to analyze the relationships between lecturer level, such as attitudes toward academic success, and at the student level, such as gender, on students' development of subject interest. To achieve this, two datasets were merged and analyzed: one from a panel study of annual assessments comprising 12,116 measurement points from 5491 cooperative students in Germany, and the other from a survey of the students' lecturers from 22 different departments, using three-level growth curve modeling. The results showed a decline in subject interest over the study program and showed that academic discipline and gender explained the development of subject interest. However, lecturers' attitude to academic success was not related to their students' development of subject interest. These findings confirmed the importance of developing interest programs for students to keep interest high.