This paper aims to investigate the up-to-date functions and features offered in PHR systems, that might affect PHR adoption, engagement, and usability. Article search was conducted in the Scopus, Medline, and Web of Science databases and 19 articles were selected in the review based on the inclusion criteria. These studies examined PHR (Personal Health Record) functionality, features, and adoption by using different research methods. As a result of the review, PHR functions were classified into 8 themes (personal information management, communication, medication, laboratory, appointment management, self-monitoring, education & advanced functions) which may impact patients' acceptance and usability of PHRs. It was found that system functionalities affect the utilisation of the patient portal, and PHR adoption and usability significantly improves when users seek and use features.