The effects of solution-treatment temperature, spinodal decomposition and plastic deformation on the magnetic domains of duplex stainless steel have been investigated. The domain structure is maze-like with spikes and these are not artefacts (unlike Fe-Ga alloys). In the solution-treatment temperature range, the domain structure does not have a big temperature-dependence. Both spinodal decomposition and plastic deformation lead to inhomogeneity and a reduction in size in magnetic domains. However, inhomogeneity in domain structure, among grains or within the same grain, may also exist in the solution-treated condition, albeit to a lesser extent. The maze-like domain structure is unaffected by the change in dislocation structure. © 2012 Elsevier Inc.