Despite supply chain revolution of the past decades, garments industries in Bangladesh struggle with production and shipment delays. Modelling of supply chain of ready‐made garments in Bangladesh is a challenge in our socio‐economic conditions because supply chain of garments is constrained by the availability of raw material, cotton, yarn, fabrics, and transportation facility. This research presents a system dynamics model of supply chain of garments in Bangladesh that is structured with inventory adjustment and demand driven to provide the right quantity at the right time at the right place. Verbal description, causal loop diagram, and stock flow diagram are hypothesized to generate the observed behaviour of ready‐made garments. Sensitivity analysis and stability of the model have also been addressed. Also, the model has been simulated to address the issue of the raw materials price instability and the policy issue of local supply of all the fabrics as well as local supply of all the fabrics with no transportation delay.