The Theory of Planned Behavior (TPB) has been widely established and most applicable to be used in any research dedicated to predict intention and behavior. Though it is one of the most cited theory in predicting intention, however recently, this theory has evidenced many attempts to deliberate and diversify its three main constructs of Attitude, Subjective Norms and Perceived Behavioral control. This article discuses on the evidence of the extension of the theory, invented by many researchers in an effort to better predict and understand intention by using additional relevant external factors.