The millennial (the 1980s and 2000 generation), is strongly influenced by digital advancements and trends, including online shopping. Online shopping platforms in Indonesia have taken advantage of offering a paylater service, gaining consumers’ interest in purchasing items using an instalment system. This research aims to examine the influence of “Financial Literacy,” “Locus of Control,” and “Lifestyle” on millennials’ financial management behavior, both simultaneously and partially, specifically among paylater users. This quantitative research was analyzed from 100 respondents using the multiple linear regression method to determine the influence between variables. The findings reveal that financial literacy, locus of control, and lifestyle significantly influence millennials’ financial management system both partially and simultaneously. They imply that financial literacy, locus of control, and lifestyle are crucial to successfully managing individual finances.