Although the Community of Inquiry is a widely used instructional model for online and blended learning, there is a lack of comprehensive research on its effects on learner motivation. This study examines the relationship between CoI presences--teaching presence, social presence, and cognitive presence--and autonomous motivation in blended learning, as well as the mediating role of basic psychological need satisfaction. Data collected from 466 students at a university and two colleges in the Maldives was analysed using structural equation modelling. The findings show that Community of Inquiry presences significantly influence basic psychological need satisfaction and autonomous motivation. Teaching presence affects BPNS directly and also indirectly through social and cognitive presence. Basic psychological need satisfaction fully mediates the relationships between teaching presence and autonomous motivation and social presence and autonomous motivation. Cognitive presence has both direct and indirect effects on autonomous motivation mediated by basic psychological need satisfaction. These results provide valuable insights into the Community of Inquiry framework, students' basic psychological need satisfaction, and self-determined motivation in blended learning environments.