Cloud computing is a new technological paradigm that offers very powerful computing and cost effective, scalable network services to its end-users / organizations without considering the firm size. Aim of this study is to review systematically the influential adopting factors of Software as a Service (SaaS) by Small and Medium Enterprises (SMEs). Thirty-three research papers have been reviewed attentively from different quality journals and valid conference reports which were published on integration of SaaS and Cloud Computing in SMEs. Increasing number of studies conducted in the last half decade on the factor adoption reflects that organizations whether small or medium are very eager and enthusiastic to integrate SaaS framework in order to get competitive advantages and proliferation of business. Findings of this study segregated innovation variables and recapped TOE as I-TOE (innovational, technological, organizational and environmental perspectives) are the most influential adopting factors of SaaS in the context of SMEs.