The spatial structure of urban areas is a critical factor in their efficiency, spatial equity and consequently, sustainability. Monocentric urban structures are often characterised by longer commutes and inner-city congestion, which threaten urban sustainability. The Western Australian government has embarked on an employment decentralisation agenda aimed at bringing jobs closer to the people and improving urban sustainability in the Perth Metropolitan Region. This study employs density and accessibility measures to evaluate this decentralisation (or rather ‘poly-centralisation’) policy. Firstly, it investigates the spatial patterns of labour and job densities and their ability to support suburban activity centres (ACs). Secondly, it investigates potential improvements in the level of job accessibility in and around ACs, which could be delivered by the policy’s employment targets. The results reveal that while the car enables larger catchment areas for ACs, the average densities within these catchments are lower than in those enabled by public transport. Accessibility in AC areas is generally poor, and the current policy targets for jobs at ACs will not change the functional spatial structure, improve accessibility equity or the overall travel patterns within the metropolitan area. Despite having better transport connectivity, there are many other zones within the study area with higher accessibility than the designated AC zones. Results of this work can guide long-term planning by identifying potential/alternative areas to be targeted for densification, as well as those ACs that might require more transport infrastructure investment to compensate for their locational disadvantage.