Scholars generally argue that nationalism and secessionism pose important dilemmas for national, regional and global order. Yet, there is inadequate discussion on the varied contexts of nationalist secessionist movements and how they influence or are influenced by domestic and global forces. Addressing this concern, this article undertakes a three‐case comparison of the Western Togoland separatist movement in Ghana, Southwest and Northwest (Anglophone) Cameroon's secessionist movement and the movement for independent Catalonia in Spain. These dissimilar cases—both from Global South and North—enable a broader examination of how themes such as political history, state capacity and regional/continental organisations affect nationalist‐induced secessionist movements and the measures to address them. Using a thematic comparative approach, this article examines the relevant literature on secessionism, nationalism, regionalism and cognate fields to demonstrate that the dynamics and consequence of secessionist movements depend largely on four interwoven factors: (a) the internal organisation and support for the nationalists' course, (b) state capacity to handle uprisings, (c) political conditions and conflict context of neighbouring countries and (d) interest and (re)actions of regional bodies and international allies. The comparative approach thus offers nuance, illustrating the critical angles of variations and intersections in secessionist movements and the effect on global order.