The present research examined the role persistence plays in mediating the positive impact of memory self-efficacy (MSE, i.e., one’s confidence in one’s own memory abilities) on older adults’ memory performance. In three studies, 81 to 264 older adults completed an MSE scale and carried out an explicit episodic memory task, during which we recorded their study time as an indicator of task persistence. We found that higher MSE was indirectly related to better memory performance through greater persistence during encoding, as measured by longer study time. Indirect effects were of medium size, with point estimates ranging from 0.64 to 0.85. This mediation effect was independent of factors that could be confounded with study time: chronological age, memory span, prior level of memory performance, episodic memory ability, and use of learning strategies (encoding strategies and self-testing). When confronted with difficult memory tasks, older adults who lack confidence in their memory abilities cease their efforts prematurely, which contributes to a decrease in their performance. Encouraging older adults to persist in the face of difficulties during encoding and retrieval may help alleviate the negative impact of low MSE on memory performance and allow researchers and clinicians to more accurately estimate older adults’ true memory abilities.