Advances in transportation and communication have resulted in the ease of migration of people across transnational borders and the internationalisation of business organisations. These events have brought about changing workforce demographics, intense global competition, and the quest for talents across the world. These trends have made workforce diversity inevitable for transnational companies (TNCs). TNCs operating in Nigeria face a peculiar problem as there are two layers of ethnic diversity created by the country’s enormous diversity. The task of managing the layers of diversity is complicated by the weak legal and institutional provisions for the management of diversity in public and private firms. Also, there is a general lack of awareness about diversity and inclusion (D&I) in Nigeria; hence, the field has received scant attention from academics and practitioners. This study explored the D&I policies and strategies adopted by selected subsidiaries of TNCs in Nigeria and describes ethnic minority employee perception of D&I policies and the effects these policies have on performance at the individual and team levels. To achieve these objectives, it aims to provide answers to two research questions: “What are the organisational policies and strategies that enhance diversity and the inclusion of ethnic minority employees in TNCs; and how do D&I policies and strategies impact the performance of individuals and groups within the organisation?” The study adopted the exploratory mixed-methods design to collect qualitative and quantitative data for analysis. The qualitative data included the primary and secondary sources; and involved semi-structured interviews with six senior managers in four subsidiaries of TNCs and documentary analysis. While the quantitative data involved a survey of 133 employees across the four participating companies. The reflexive thematic analysis method was used to analyse the qualitative data, leading to the generation of themes; while the quantitative data were analysed using the descriptive statistical technique. Findings reveal the presence of varying degrees of D&I initiatives among the participating organisations, ranging from well-articulated and established programmes in one company to medium range policies in two companies, and no initiatives in one company. Findings also suggest a high level of inclusion of ethnic minority employees at the group or team level and a low inclusion at the top management level. Also, participants generally report a positive perception of the relationship between workforce D&I and performance at both the individual and team level. Some of the variables used to indicate inclusion are access to information, participation in group activities, membership of informal networks, participation in decision-making and participation in meeting with supervisor and senior management. Similarly, some of the performance variables include creativity, innovation, timely completion of tasks and quality of work output. Finally, the findings from the study contributed to filling the gap in the literature as well as empirically highlighting the D&I policies operational in TNCs in Nigeria. The study recommends that diversity policy-makers pay attention to the additional layer of diversity while developing global policies for a more inclusive organisational environment. This study has provided valuable insights into the policies and practices as well as employee perception of diversity in light of the dearth of studies from the Nigerian context. Despite some inherent limitations, it serves as a starting point that could ignite the interest of other researchers and practitioners in the fields of diversity. / Tertiary Education Trust Fund (TETFund)