Traditional finance assumes people to be rational and ignores the psychological and emotional factors that influence their decisions and behaviors. Behavioral finance is where psychology and finance science meet on common grounds and does not accept the rational human assumption of traditional finance, because various psychological biases exist that affect people’s decisions. The aim of this study is to investigate in the context of behavioral finance whether any differences exist between the biases that affect the financial decisions of participation bank customers and traditional bank customers throughout Türkiye. The study used a questionnaire to collect data from a total of 855 participants and performed frequency analyses, validity and reliability analyses, and descriptive statistics based on the survey data. The study then used the non-parametric Mann-Whitney U test to test the hypotheses. The results show behavioral finance biases to affect the financial decisions of participation bank customers and traditional bank customers and both bank groups to be broadly similar in terms of the financial biases that influence customers’ financial decisions. The study has unique value in that it provides the opportunity to compare the biases that affect the financial decisions of Islamic bank customers and traditional bank customers in the context of behavioral finance.