This article explores the possibility of conceiving South America and Southern Africa as subsystemic unipolarities under Brazilian and South African primacy, respectively. It argues that this concept, when applied to these regions, sheds light not only on the long-term strategies behind the Brazilian and South African foreign policies towards their neighbourhood, but also on the behaviour of secondary regional powers and small states. This hypothesis questions the maxim that considerations related to polarity affect great powers only. After examining the Brazilian and South African cases, the author undertakes a comparative analysis of 17 countries in these regions, showing that the behaviour of politically stable countries in these regions is as predicted by theories of unipolarity.