Environmental plastic wastes are continuously degraded into microplastics (MPs) and nanoplastics (NPs); the latter are more potentially harmful to organisms and human health as their smaller size and higher surface-to-volume ratio. Previous reviews on NPs mainly concentrate on specific aspects, such as sources, environmental behavior, and toxicological effects, but few focused on NPs-related scientific publications from a global point of view. Therefore, this bibliometric study aims to summarize the research themes and trends on NPs and also propose potential directions for future inquiry. Related papers were downloaded from the Web of Science Core Collection database on NPs published from 2008 to 2021, and then retrieved information was analyzed using CiteSpace 6.1 R2 and VOSviewer (version 1.6.). Research on NPs mainly involved environmental behaviors, toxicological effects, identification and extraction of NPs, whereas aquatic environments, especially marine systems, attracted more attentions from these scientists compare to terrestrial environments. Furthermore, the adsorption behavior of pollutants by NPs and the toxicological effects of organisms exposed to NPs are the present hotspots, while the regulation of humic acid (HA) on NPs behaviors and the environmental behavior of NPs in freshwater, like rivers and lakes, are the frontier areas of research. This study also explored the possible opportunities and challenges that may be faced in NPs research, which provide a valuable summary and outlook for ongoing NPs-related research, which may be of intrigue and noteworthiness for relevant researchers.