Abstract: This study employed a sentence-final word judgment paradigm, combined with event-related potentials (ERPs) and sLORETA source localization, to examine how context, conventionality, and age modulate metonymy comprehension in Mandarin-speaking children aged 6 to 11. The results showed that metonymic sentences elicited larger N400 amplitudes than literal sentences, suggesting greater demands on semantic retrieval and integration during metonymic meaning access. Contextual cues were associated with modulations in P200, N400, and LPC, indicating that context contributes to both early semantic anticipation and later meaning integration. The effect of conventionality was not unidirectional but was jointly shaped by context, sentence type, and age, suggesting that conventional and novel metonymies may involve different patterns of semantic processing. Age-related differences were mainly reflected in patterns of neural resource allocation: children aged 6 to 8 showed broader involvement of fronto-temporal regions, whereas children aged 9 to 11 exhibited a relatively more focused pattern of semantic integration. These findings suggest that the development of children’s metonymy comprehension involves a shift from greater reliance on explicit contextual support to more stable pragmatic inferencing, providing neurocognitive evidence for research on children’s non-literal language processing and related assessment tasks.