This study examined mathematics self-efficacy and the characteristics of flow in the context of performing mathematical tasks. In particular, it explored the subjective experiences of 113 undergraduate students enrolled in a developmental mathematics course while they were independently solving certain mathematical problems. This study supplemented the literature on the role of self-efficacy as a mediator of the effect of the challenge/skill ratio on flow by applying it to the context of mathematical problem solving. This study also expanded the discussion on how findings may indicate a direction for further research on mathematics anxiety. Additionally, the relationship between mathematics self-efficacy and flow-like experiences as measured by the Flow Short Scale was considered.