Abstract: A standard economic model (i.e., Theory of Planned Behavior) is based largely on logical cognition (Ajzen & Fishbein ,1991). As a result, it is known for the rational component in the theory predominates in influencing the dependent variable that is intention; meaning that, TPB largely ignores the role of irrational influences in decision making. However, in reality, an individual decision is based on both rational and irrational forces (Micklitz et al., 2011; Mullainathan & Thaler, 2000). The study, being explorative, include Cognitive Bias as a moderator to predict female consumers purchase intention towards cosmetic products choice paradox. Hence, to the extent that it can incorporate the measurement of irrational variation, this study postulates that TPB can be improved as a model of behavioural intention. A selfadministered questionnaire was employed to gather data from 380 consumers via purposive sampling and subsequently analysed using Partial Least Squares–Structural Equation Modeling (PLS-SEM). This study attempts to investigate if Cognitive Bias which is known as an irrational factor moderates, that is, either improves or reduces purchase decision of consumers due to the causal effects of Behavioral Beliefs and Attitude. As a result, it has been found that people's decision making is heavily influenced by the framing of the problem which is known as Cognitive Bias (van Schie & van der Pligt, 1995; Elliot & Archibald, 1989; Tversky & Kahneman, 1981); thus, Cognitive Bias violates Expected Utility Theory.