One of the most important factors that makes the transition from secondary school to medical school challenging is the inability to put in the study time that a medical school curriculum demands. The implementation of regulated learning is essential for students to cope with medical course environment and succeed. This study aimed to investigate the reciprocal relationships between self-regulated learning skills (SRLS) and academic workload (AW) across secondary school to medical school transition. Freshmen enrolled in medical school (N = 102) completed questionnaires at the beginning and at the end of their academic year, assessing AW (measured as study time hours and perceived workload), SRLS (planning and strategies for learning assessment, motivation and action to learning and self-directedness) and academic achievement. An exploratory factor analysis (EFA) and a longitudinal path analysis were performed. According to the EFA, study time and perceived workload revealed two factors of AW: students who had a high perceived workload also demonstrated increased study time (tandem AW); and those who had a low perceived workload also demonstrated increased study time (inverse AW). Only a longitudinal relationship between SRLS and AW was found in the path analysis: prior self-directedness was related to later tandem AW. Moreover, success during the first year of medical school is dependent on exposure to motivation, self-directedness and high study time without overload during secondary school and medical school, and prior academic achievement. By better understanding these relationships, teachers can create conditions that support academic success during the first year medical school.