Challenges faced in public e-procurement implementation are not well understood despite past studies focusing on the phenomenon. This paper, which is based on a systematic literature review of academic papers, seeks to synthesize and examine the key challenges impeding public e-procurement implementation. These challenges are categorized using the Technology-Organization-Environment (TOE) framework as follows (1) Technological challenges: e-procurement acceptance and usage, disruptive innovation characteristic of e-procurement, use of digital signatures, security and privacy of technology and technical aspects of e-procurement (2) Organizational challenges: stakeholders’ behavior, leaders’ behavior, shortcomings in leadership, lack of training and skilled personnel, resistance to change, organizational power and politics and the creation of public value underlying e-procurement (3) Environmental/Contextual challenges: regulatory framework for public procurement, Small-and-Medium-Size Enterprise issues, and context of the country. Key e-procurement implementation challenges are grounded in human and contextual issues. So we recommend more case studies on public e-procurement implementation in the future.