Behavioral evidence has shown that older adults are less able to overcome proactive interference in memory than young adults. However, it is unclear what underlies this deficit. Imaging studies in the young suggest overcoming interference may require post-retrieval selection, a process thought to be mediated by the left mid-ventrolateral prefrontal cortex (VLPFC). Further, selection may resolve interference by enhancing or suppressing perceptual processing. The present fMRI study investigated whether age-related changes in VLPFC-mediated post-retrieval selection underlie older adults' deficits in overcoming interference in associative memory. Participants were tasked with remembering which associate (face or scene) objects were paired with most recently during study, under conditions of high or low proactive interference. Behavioral results demonstrated that as interference increased, memory performance decreased similarly across groups. Across groups, activity in the left mid-VLPFC also increased with interference. However, right PFC post-retrieval monitoring effects, but not left mid-VLPFC, distinguished successful vs. unsuccessful resolution of interference for both young and older adults, suggesting selection alone may be insufficient for successful resolution of interference. Age-related memory deficits may be related to reduced recruitment of relational processing effects in the dorsolateral and anterior PFC, as well as reduced memory retrieval effects in the hippocampus. Lastly, results showed evidence that selection may modulate perceptual processing of retrieved memory representations. Namely, activity in the parahippocampal place area (PPA) was greater when participants selected scene, versus face, regardless of accuracy. Further, older adults showed reduced effects in the PPA, possibly reflecting reduced differentiation of perceptual processing. Taken together, these results suggest age-related deficits in overcoming proactive interference are not related to post-retrieval selection, but reduced recruitment of PFC-mediated relational processes, coupled with reduced associative memory retrieval.