This current study examines how research themes and trends have developed in the e-commerce field, aiming to provide a comprehensive understanding of e-commerce research based on prior literature. To answer this question, the current study applied a bibliometric method, word co-occurrence (co-word) analysis, to identify core research themes and trends in the e-commerce field, based on 17,416 author-provided keywords collected from 3,284 academic articles published between 2001 and 2020 in seven major journals in e-commerce field. Specifically, the data were analyzed based on two periods: 2001–2010 and 2011–2020. We found that the research themes in the e-commerce field have evolved alongside technology’s development and diffusion. Some research themes, such as recommended system and eGovernment, have persisted as important research themes and studied continuously over the 20 years studied. Some research themes studied in 2001–2010, such as B2C and XML, disappeared in 2011–2020, whereas some new research topics, such as cloud computing, mobile technologies, artificial intelligence, and machine learning, emerged in recent years. This study provides a good understanding of e-commerce research’s evolution, as well as useful suggestions to direct future research by scholars in the e-commerce field.