The rapid growth of young investors, specifically those born between 1997 and 2012 and known as Generation Z, has significantly increased the investor population in Indonesia over the past five years. This demographic shift is largely driven by Generation Z's familiarity with advanced technologies, which facilitate easy access to investment information. However, despite their tech-savvy nature, Generation Z's propensity for impulsive decision-making often results in misguided investments and financial losses. This study aims to examine the impact of heuristic availability bias (HAB) on investment decision-making (IDM) among Generation Z investors in West Java. Additionally, it explores the moderated mediation role of external locus of control (ELC) and risk tolerance (RT) within this context. The methodology involved a quantitative approach, using a survey to collect data from a sample of 420 Generation Z investors in West Java. The data were analyzed using SPSS PROCESS Model 7 (moderated mediation) The results reveal significant interactions between HAB, RT, and ELC, indicating that while heuristic availability bias directly influences investment decisions, this effect is moderated by individuals' risk tolerance and mediated by their external locus of control. These findings highlight the complex dynamics that influence investment decisions in this demographic.