Seagrass and seagrass meadow ecosystems and their adjacent environment are important parts of the offshore marine ecosystem and serve many important ecological service functions. Compared with mangroves and coral reefs, scientists and the public pay less attention to seagrass, and knowledge of the current status, trends, and hotspots gained from international seagrass research are limited. The literature regarding seagrass research was retrieved from the Web of Science's SCI-E database from 1983 to 2017 and bibliometric information visualization analysis methods were applied to conduct a systematic bibliometric assessment of annual publications, research strength, research hotspots, and topics. The goals of this study were to clarify the trends and hotspots of international seagrass research, and to generate valuable reference information for related researchers. The results showed that the amount of international seagrass research literature exhibited an obvious upward trend from 1983 to 2017. The top three countries in this field are the United States, Australia, and Spain. The institution with the most publications was Florida State University, followed by the Spanish National Research Council and National Oceanic (Consejo Superior De Investigaciones Cientificas, CSIC), and the National Oceanic and Atmospheric Administration (NOAA). Authors with a relatively larger total number of publications were Duarte CM, Marba N, and Fourqurean JW; Santos R had the greatest number of publications in the past three years. The most frequently listed journals were the Marine Ecology Progress Series, Aquatic Botany, and Estuarine; Limnology and Oceanography had the highest impact factor (3.969) of the top 15 journals. In cooperation with countries, institutions, and authors, Spain, Denmark, the Netherlands, and Mexico formed a close cooperation network. CSIC and NOAA were two centers in the cooperation network of institutions. Duarte CM, Marba N, and many other scholars exhibited close academic cooperation. The three hot topics of seagrass research were summarized through the analysis of association of high-frequency keywords, and were the effects of environmental stress (pollution) on seagrass meadows, growth and physiological ecology of seagrass, structure and function of seagrass and its related ecosystems. The Chinese Academy of Sciences, Ocean University of China, and other institutions have made important contributions to the study of seagrass in China. Because of the later start of seagrass research, there is a gap between scholars in China and those in European and American countries regarding the number of publications and average citations per article. However, the literatures published in recent years has increased rapidly. It is expected that there will be a strong developmental trend in seagrass research in the future.