The effect of social support on academic procrastination among health professions students and its potential mechanism are yet to be fully explored. A serial mediation model informed by self-determination theory (SDT), was here established to explore that effect, as well as the mediating roles of academic self-efficacy and intrinsic learning motivation. This cross-sectional study involved 596 health professions students enrolled in different majors at a university in Shenyang, China. Data were collected through a questionnaire assessing basic demographic information, social support, academic procrastination, intrinsic learning motivation, and academic self-efficacy. Social support was found to be negatively correlated with academic procrastination. Intrinsic learning motivation and academic self-efficacy were both mediators that partially and jointly mediated the relationship between social support and academic procrastination. These results suggest that multifaceted social and educational interventions aimed at improving social support, intrinsic learning motivation and academic self-efficacy can reduce academic procrastination among health professions students.