Ika Yanuarti LoebiantoroCham Tat Huei0000-0003-0601-0325Eaw Hooi ChengNursyamilah AnnuarSanjar Mirzaliev2025-10-152025-10-152025-03-1810.14707/ajbr.250191https://dspace-cris.utar.edu.my/handle/123456789/11494Investors’ decisions are often influenced by behavioural biases like the availability bias and the disposition effect, which are shaped by personality traits such as openness, conscientiousness, extraversion, agreeableness, and neuroticism. This study investigates how these traits impact these biases, drawing from Bounded Rationality Theory and Dual Process Theory, which suggest that investment decisions blend rational (cognitive) and irrational (intuitive) elements. Using a quantitative approach with 716 participants, the data was analysed through the structural equation modelling (SEM) statistical technique using SmartPLS. Findings reveal that availability bias is positively influenced by openness and agreeableness. Conversely, the disposition effect is positively associated with openness, extraversion, and agreeableness. Investors who exhibit high levels of openness, extraversion, and agreeableness typically base their decisions on available information, often selling profitable stocks and holding onto declining ones, which can result in investment losses. Identifying these biases is crucial for investors, managers, and regulators as they navigate investment decisions effectively. © 2025, Asia Business Research Corporation. All rights reserved.enAgreeablenessConscientiousnessConsumer behaviourExtraversionNeuroticismOpennessjournal-article