First-year failure rates remain a persistent equity challenge in university mathematics, with female and first-generation students disproportionately affected. These disparities motivate the exploration of pedagogical approaches that support diverse learners during the critical transition to university mathematics. The flipped classroom, combining independent pre-class preparation with collaborative in-class work, holds promise for improving student achievement. However, evidence of its effectiveness in undergraduate mathematics remains inconclusive, and existing literature focuses on quantitative performance-related measures rather than equity-related outcomes. One such study is that of Hardebolle et al. [2], a large-scale evaluation of a flipped first-year Linear Algebra course. Although there were no overall performance gains, the flipped format produced equity benefits: gender gaps were reduced and reversed, and students with weaker mathematical backgrounds improved significantly. The underlying mechanisms, however, remain unexplored. Qualitative evidence capable of illuminating the cognitive, social or affective processes through which the flipped classroom influences learning is lacking. This study investigates how students’ experiences in the flipped classroom shape mathematical self-efficacy, a key predictor of first-year achievement and persistence. It further examines how these experiences vary across groups defined by gender, first-generation status and prior mathematical preparation. To capture lived experiences, semi-structured interviews with 20 purposively sampled first-year students enrolled in the flipped Linear Algebra course, complemented by an instructor interview, are analysed using thematic analysis guided by Bandura’s self-efficacy theory [1]. Findings are reported through this framework. Collaborative problem-solving, in-class practice, and structured feedback in the flipped classroom promote mathematical self-efficacy by increasing mastery experiences, social learning, and positive emotions. These mechanisms are particularly salient for students who enter the course reporting lower confidence. By providing a qualitative account of students’ confidence, emotional responses, and social interactions in the flipped classroom, this study explains observed equity gains and aims to inform the design of inclusive undergraduate mathematics instruction.