While much research has focused on consumer and technological aspects of cashless payment systems, fewer studies address this topic from the merchants’ perspective. This study examines the factors influencing merchants’ adoption of cashless payment systems using the Technology-Organization-Environment (TOE) framework. Through a systematic review of 33 relevant studies, it synthesizes key insights into how technological factors (e.g., compatibility, perceived usefulness, and security), organizational factors (e.g., knowledge and skills, cost and revenue, merchant background, and perceived trust), and environmental factors (e.g., customer demand, competitive pressure, policies, and regulations) shape merchants’ adoption decisions. This paper highlights the interrelated nature of these factors, providing a holistic understanding of cashless payment systems adoption. Using the TOE framework, this review categorizes internal and external influences while offering theoretical insights into their complex interplay across contexts. The findings are valuable for businesses, regulators, payment service providers, and payment infrastructure developers seeking to promote cashless payment adoption among merchants.