Adopting a psycho-sociopolitical approach, the present paper describes the results of a community-based participatory needs assessment focusing on the perceived needs of women of reproductive age as users of primary healthcare in contexts of migration-driven diversity and socioeconomic vulnerability in the Metropolitan Area of Lisbon. The investigation comprised 64 in-depth interviews with women, including natives and immigrants to Portugal from the main origin countries in the context under study (Brazil, Cape Verde, and other Portuguese-speaking African countries) and a survey of 125 women, again natives and immigrants from these countries. The central role of qualitative methodology and grounded theory, in the framework of a multi-method research, allowed understanding the needs of women as embedded in contexts characterized by asymmetrical power relations, in terms of unequal opportunities and resources, at multiple interrelated ecological levels (personal, relational, organizational, community, socioeconomic, health system/policy, cultural/migration). The priority perceived needs of women were primarily related to socioeconomic disadvantage, severely aggravated in the current contexts of crisis; and factors at the health system level, mainly unequal access to family doctors, excessive waiting lists, and increases in the direct costs of healthcare. Results allow questioning the adequacy of cultural competence approaches for the reduction of inequalities in maternal-child healthcare in the context under study, showing the critical and innovative value of qualitative methodology and grounded theory in research on social justice and health in contexts of diversity characterized by unequal power dynamics.