This study explores the relevance of the core–periphery relationship in the Southern African Customs Union (SACU), a union comprising five highly unequal economies. In the analysis, the study employs five key indicators: economic size, trade logistics and facilitation, regional integration, and intra-SACU trade, to assess the main aspects underlying the core–periphery relationship in the union. The findings of this study point to dominance-dependency behavior within the union, where South Africa is the dominant core while Botswana, Lesotho, Namibia, and eSwatini are the dependent periphery. Based on the findings, the recommendations are that SACU countries should, among other strategies, identify ways of promoting high-value-added cross-border value chains across the union members. Also, the Botswana, Lesotho, Namibia, and eSwatini peripheries could improve their infrastructure and productive capacity if their objective is to create an export base in some of the products currently supplied by South Africa.