Abstract: Investment decisions are usually influenced by various behavioural factors. The assumption is that herding, prospecting and heuristics influence personal investment decisions among investors in the stock market. The main objective of this study was to analyze the behavioral factors influencing investment performance of individual investors in Nairobi Security Exchange. The specific objectives of the study were; assess whether the following factors-herding, prospect (loss aversion, regret aversion, and escalating the commitment), heuristic (availability bias and overconfidence) and investment decisions-are significantly correlated with each other in the NSE and establish whether the following behavioural factors-herding, prospect (loss aversion, regret aversion, and escalating the commitment) and heuristic (availability bias and overconfidence) combined together significantly influence the investment performance in the NSE