Introduction: Motivation plays a crucial role in the academic success and professional development of medical students. Understanding the intricacies of motivation within the context of medical education is essential for designing effective interventions and support systems. The aim of this study was to explore the adaptation of the Academic Motivation Scale within the framework of the self-determination theory and of the self-efficacy theory to assess motivation among medical students.Methods: The study adapted the Academic Motivation Scale to the Portuguese context, drawing upon insights from the self-determination theory. Two existing Portuguese scales, MATAMS and Ribeiro et al scale, served as foundational frameworks for the adaptation process. The study included qualitative interviews, which informed the creation of the Minho Medical Academic Motivation Scale – Minho-MEDAMS. This scale was applied to 281 medical students. To assess the scale’s validity, we used the exploratory and confirmatory factor analyses, and the Cronbach’s alpha to measure internal consistency.Results: The exploratory factor analysis showed strong results with a KMO of 0.862, leading to five factors and the removal of two items. The initial confirmatory factor analysis indicated poor fit, prompting the removal of items with low R-squared values. The final Minho-MEDAMS includes 18 items: six for intrinsic motivation, nine for extrinsic motivation and three for amotivation. This refined scale demonstrates high internal consistency (α = 0.831), making it a reliable tool for assessing medical students’ motivation.Conclusion: The successful adaptation of the Academic Motivation Scale within the self-determination theory framework presents a valuable instrument for assessing motivation in medical students. The Minho-MEDAMS offers a comprehensive understanding of motivational dynamics, facilitating targeted interventions and support mechanisms to enhance student engagement and success. Its validity and reliability render it a practical tool for educators, administrators, and researchers in the field of medical education. Ultimately, the Minho-MEDAMS contributes to the advancement of strategies aimed at cultivating motivated and proficient healthcare professionals.