1,3-Diiodotetrafluorobenzene and 1,3,5-trifluoro-2,4,6-triiodobenzene form co-crystals with 4,4′,6,6′-tetramethyl-2,2′-bipyrimidine, 1,2,4,5-tetra(3-pyridyl)benzene and 1,2,4,5-tetra(4-pyridyl)benzene in which the structural competition between π⋯π interactions and halogen bonds is directly observed. It is found that the strong C–I⋯N halogen bond competes successfully with the π⋯π interaction between two 1,3-diiodotetrafluorobenzene molecules while the π⋯π interaction between two 1,3,5-trifluoro-2,4,6-triiodobenzene molecules can successfully compete with the strong C–I⋯N halogen bond. Quantum chemical calculations explain the structural competition well.