Few studies have examined global foreign accent (GFA) in bilingual children, and little is known about how GFA changes over time and what factors determine change. Here, we examine GFA trajectories in Japanese-English bilingual returnees (Japanese children who returned to Japan after having lived in a majority English environment for several years). In two accent-rating tasks, first language (L1) speakers of English or Japanese rated returnee speech excerpts recorded at three time points over a five-year period. The ratings show a decrease in Japanese GFA one year after return to Japan, and an increase in English GFA, but only five years after return. These findings suggest rapid re-exposure effects of the L1 and relatively stable maintenance of the second language (L2). Changes varied by L2 English age of onset (AoO) and exposure to L2 English while abroad, suggesting a crucial role for these individual factors in transitory contexts such as returnee bilingualism.