There is a great interest in both outsourcing and insourcing as globalization of IT services takes place. As companies started to embark on IT outsourcing, IT Insourcing is significantly attaining equivalent level of attention. More explicitly, there is limited number of research in IT Insourcing or do not critically examine the factors that influences this strategic decision. Therefore, it is imperative to scrutinize the numerous factors that possibly will influence the IT Insourcing decision of corporate companies in Malaysia. The independent variables encompass cost, capability, quality, environment and strategic value. The theories that are emphasized in this research are Transaction Cost Theory (TCT), Resource Based View Theory (RBT), Dynamic Capability Theory (DCT) and Institutional (Based) Theory (IBT). The association amid the theories is established through various tests of model reliability and validity. The Confirmatory Factor Analysis (CFA) and Multiple Regression Modeling are used to analyze the data and validate the hypotheses. This research is conducted in Klang-Valley (geographical area in Peninsular Malaysia), Malaysia consisting of companies from Oil & Gas and Financial Industry. The data collection is conducted using a self-administered questionnaire where response is measured using 5-point Likert scale. The research is conducted between the period of July and August 2017. A sample size of 130 is selected using Probability Convenient Sampling. Total of 130 samples collected and analyzed. The responses collected are logged and coded into SPSS and AMOS for analysis. The results revealed that cost, capability and environment have significant positive impact on IT Insourcing. The results also revealed that quality and strategic value have insignificant impact on IT Insourcing. The research is expected to provide insight to corporate companies on the factors to consider as part of the strategic decision making before embarking on IT Insourcing.