The microbial colonisers of plastics – the ‘plastisphere’ – can affect all interactions that plastics have with their surrounding environments. While only specifically characterised within the last 10 years, at the beginning of 2021 there were 140 primary research and 65 review articles that investigate at least one aspect of the plastisphere. We gathered information on the locations and methodologies used by each of the primary research articles, highlighting several aspects of plastisphere research that remain understudied: (i) the non-bacterial plastisphere constituents; (ii) the mechanisms used to degrade plastics by marine isolates or communities; (iii) the capacity for plastisphere members to be pathogenic or carry antimicrobial resistance genes; and (iv) meta-OMIC characterisations of the plastisphere. We have also summarised the topics covered by the existing plastisphere review articles, identifying areas that have received less attention to date – most of which are in line with the areas that have fewer primary research articles. Therefore, in addition to providing an overview of some fundamental topics such as biodegradation and community assembly, we discuss the importance of eukaryotes in shaping the plastisphere, potential pathogens carried by plastics and the impact of the plastisphere on plastic transport and biogeochemical cycling. Finally, we summarise the future directions suggested by the reviews that we have evaluated and suggest other key research questions.