Our paper explored the impact of demographic variables on the manifestation of behavioral biases among Nepalese portfolio investors as they make investment decisions. Our research analyzed the relationship between age, gender, and experience, and five common biases such as overconfidence, anchoring, herding, loss aversion, and hindsight. Our survey of 132 investors revealed that demographic factors play a role in the presence of these biases, with female investors exhibiting higher overconfidence and anchoring biases, while male investors displayed loss aversion, herding, and hindsight biases. Younger investors were found to be more overconfident and prone to loss aversion, whereas more experienced investor demonstrated greater overconfidence in their analysis skills. This paper provides crucial insight into the importance of considering demographic factors in addressing investment decision-making biases. It’s worth noting that the responses and sample location may not be fully representative.