The neural correlates of encoding mode, or the state of forming new memory episodes, have been found to change with age and mnemonic training. However, it is unclear whether neural correlates of encoding success, termed subsequent memory (SM) effects, also differ by age and mnemonic skill. In a multi-session training study, we investigated whether SM effects are altered by instruction and training in a mnemonic skill, and whether such alterations differ among children, younger adults, and older adults. Before and after strategy training, fMRI data were collected while participants were memorizing word pairs. In all age groups, participants receiving training showed greater performance gains than control group participants. Analysis of task-relevant regions showed training-induced reductions in SM effects in left frontal regions. Reductions in SM effects largely generalized across age, and primarily reflected greater training-induced activation increases for omissions than for remembered items, indicating that training resulted in more consistent use of the mnemonic strategy. The present results reveal no major age differences in SM effects in children, younger adults, and older adults. Thus, these regions were targeted in the present research.Moreover, all age-comparative training research using brain imaging has investigated training-related changes in encoding mode, which refers to changes in activity differences between an attempt to remember information (independent from 4 success) and a no-memory explicit baseline (i.e., a task similar in visual complexity to the memory task that only requires simple perceptual decisions; Jones et al., 2006; Kirchhoff, Anderson, Barch, & Jacoby, 2012; Nyberg et al., 2003). In contrast, encoding success refers to the contrast between remembered and not-remembered information (i.e., omission errors), and thus helps to identify regions that are relevant to successful memory formation. In functional magnetic resonance imaging (fMRI), subsequent memory (SM) effects refer to regional activation differences during encoding of trials that are later retrieved successfully and encoding of trials that are not retrieved. The present study investigates whether SM effects are altered by instruction and training in a mnemonic skill, and whether such alterations, if present, differ among children, younger adults, and older adults.We used a cued-recall paradigm to investigate EM performance before and after mnemonic strategy instruction and training. Individuals were scanned during encoding of word pairs. We expected training-related performance changes for all three age groups in comparison to age-matched controls. As SM effects focus on the relation between remembered and not-remembered information and not on the level of activation per se, it is conceivable that differences between remembered and notremembered items are reduced after strategy training. This is so because activations for remembered and not-remembered information may become more similar after training, reflecting...