This paper examines the effect of cognitive biases on investment decisions in Okara, Pakistan. It analyzes the impact of five biases: availability, anchoring, overconfidence, herd instinct, and regret aversion. The study finds availability, overconfidence, and herd instinct biases positively correlate with irrational investment decisions, while anchoring and regret aversion do not. Of the biases, overconfidence has the strongest impact. The paper concludes investors and policymakers should address cognitive biases through de-biasing methods to improve investment decision making.