Academic procrastination has a significant influence on students' lives, being related to several relevant variables, such as lower self-esteem, higher levels of academic anxiety, and fear of failure. The development and adaptation of reliable instruments help to assure a more in-depth study of academic procrastination. The present research aimed to adapt and assess evidence of validity and reliability of the scores of the Academic Procrastination Scale (APS) for a Brazilian sample (N = 1241). In Study 1, an exploratory factor analysis supported the unidimensional structure of the APS (25 items). In Study 2, the one-factor structure had an adequate model fit via confirmatory factor analysis. Also, through item response theory, the APS items showed adequate discrimination, difficulty, and level of information. The scores of the APS were also significantly correlated with the scores of the Tuckman Procrastination Scale, providing evidence of convergent validity.