Abstract The post‐Cold War world‐system into which post‐apartheid South Africa is being inducted is essentially unstable. The current global trend towards regionalism calls for a careful assessment of South Africa's foreign policy options in the ‘new world order’. This paper makes a case for complementary regionalism between West and Southern African sub‐regions, especially in the areas of economy, ecology, strategic relations and governance. It contends that notwithstanding the objective and subjective limitations to their capabilities, and a history of political antinomies, the Republic of South Africa and Nigeria would be crucial to any future efforts to achieve continent‐wide regionalism in these four important aspects, hence the need for greater cooperation between them.