Mega-city regions (MCRs) embody the robust economic growth experienced in Asia in the 21st century. Super MCRs (sMCRs) have developed due to continuous metropolisation extending deep into surrounding hinterlands. This paper examines the suburbanisation and functional specialisation processes in a typical sMCR in China: the Pearl River Delta (PRD). Applying principal component analysis and change importance values, shifting patterns in the socioeconomic structure of the PRD between 2000 and 2020 are analysed and compared using county/district-level occupational data. The nuanced findings show that the suburbanisation process in the PRD during the research period included manufacturing activities and tertiarisation. Sub-central areas have become increasingly important and functionally specific as the location for knowledge-intensive business services and other emerging occupational activities, such as environmental governance. These changes have contributed to the evolution of the PRD from a development pattern dominated by core cities to a polycentric sMCR with a specialised division of labour and cooperation between cities.