In the industry of Information Technology (IT) Startup, high birth rates go hand in hand with a high risk of failure; only one in three survive the first three years. There is a set of factors that influence the success of the Startup. So in this paper we present a Systematic Literature Review of critical success factors of IT Startups. Our keyword search found 1,013 papers and a total of 74 primary studies were selected and analyzed as a result of the systematic review. We identified 21 critical success factors grouped into three categories (organizational, individual and external) and 4 stages of development through which a Startup passes (seed, early, growth and expansion). In addition, we found that the experience previous start-up of the founding team and government support factors affect the seed stage; the venture capital factor affects the early stage; the clustering, technological/business capabilities of the founding team and venture capital factors affect the growth stage; and the clustering factor affects the expansion stage. There are few studies on the stages of development that a Startup undergoes, much less on the factors that affect the stages of development.