Subject and purpose of work: The article examines the use of simulation modelling as an effective research method supporting decision-making in logistics process management. The study focuses on a branch of an international logistics company in Poland facing inefficient inventory distribution and extended order-fulfilment times. Materials and methods: A computer simulation based on discrete-event modelling (DEM) was developed to reflect the real warehouse layout and picking processes. Using the FlexSim environment, 15 variants of product placement were tested, including ABC classification, assortment-group organisation, and random allocation. Results: The findings indicate that applying the ABC method—particularly based on picking frequency—reduces average order-fulfilment time by up to 17 seconds compared to the existing layout, generating significant operational savings at high order volumes. The simulation also identified process bottlenecks and improved forklift routing. Conclusions: Simulation modelling proved effective in enhancing the analysed logistics process and offers a robust foundation for further optimisation in comparable warehouse environments.