Advances in information and communication technology, in the provision of public services, have affected all aspects of electronic governance. This widespread use has resulted in vast amounts of data, which governments and other entities can collect and analyse to measure, assess and improve service interoperability. Interoperability is the ability of software to collaborate. Currently, studies on the interoperability of e-government applications are the focus of research by previous researchers to develop information and communication technology to realize the smooth exchange of information in all elements of government. This study aims to determine the development of research on interoperability in e-government by conducting an in-depth analysis of research trends and dominant themes in e-government interoperability. This research is a systematic review using VosViewer and Nvivo Qualitative Software Analysis, and both are used to uncover trending issues and research themes on e-government interoperability. This research data was obtained through the Scopus database using a search strategy to find relevant documents. The results show that research trends related to e-government interoperability issues have declined recently. In addition, this study also presents the highest citations, funding sponsors, and research connectivity between countries. Furthermore, this study also produces six dominant themes related to e-government interoperability, namely Interoperability, E-government, Systems, Technology, Data, and Services. Some of the findings produced in this study are expected to provide a comprehensive picture of research trends in e-government interoperability for researchers in the future.