The labor-market assimilation hypothesis predicts poorer initial labor-market outcomes among immigrants followed by convergence towards the outcomes of the native-born working-age population with time lived in the receiving country. The authors investigate the applicability of this hypothesis to migrant women's labor force participation in Europe. They compare labor force participation rate (LFPR) gaps between migrant and native-born women in nine European countries, and examine how these LFPR gaps change with migrant women's additional years in the receiving country. Consistent with the assimilation hypothesis, the LFPRs of migrant women in the “old” migrant-receiving countries of Western Europe begin much lower than for otherwise-comparable nativeborn women and converge, though not always completely, towards the LFPRs of nativeborn women with additional years lived in the country. In the “new” migrant-receiving countries of Southern Europe, however, the LFPRs of migrant women at all durations of residence are similar to those of native-born women. Additional descriptive evidence suggests that differences in migrant admission and integration contexts are more plausible explanations for these contrasting Southern and Western European patterns than are explanations based on immigrant women's assumed greater family-role orientations.