Assembly lines in garment industries are the basic flow oriented production systems, in which maximum production resources are assigned. In this new era of garment industries revolution, companies are struggling for remaining competitive in global market. But in Ethiopia competitiveness is still slow. In order to respond rapidly changed customer demand, firms need to enhance their productivity and efficiency. Line balancing is considered as one of effective methods in balancing complex system of production for reducing higher work in process inventories and bottleneck operations. Assembly line balancing in garments industry aims to know potential bottleneck operations in existing production system. Critical factors of the production in Tal garments manufacturing plc. was identified before assembly line balancing task for flexible line balancing system.rnThe first methodology taken to examine the current system of production was, critical factor identification using two years production report data of the Tal garments manufacturing plc. Other approach utilized was developing operator skill matrix for greater insight, qualified assignment, flexibility and versatility of the production system using Harvey balls. The third approach undertaken was, developing simulation model based on theoretical distribution of operations processing times to examine existing system performance and developing alternative simulation models. For developing the simulation model ten (10) samples of processing time observations were taken to determine the best fit distribution of processing times based on the least square error values using arena input analyzer.rnSimulation with arena volume 14.0 software was selected with maximum relevance value in terms of flexibility & versatility, repeatability, time compression, monitoring, component integration, risk avoidance and long term applicability. The first approach used to gain critical factors like, quality workmanship, machine break down and longer repair time, quality control work in process inventory, follow up/lack of supervision wrong measurement or supply from water, to be vital few using pareto analysis. This operator skill based simulation model enable to enhance productivity of machines and labors from seven (7) pieces of shirt per day to 11 and 10 pieces of shirts per day respectively. As the researcher point of integration of critical factors and operator skill based assembly line balancing method will give new insight in balancing assembly lines of garment industries in the future studies.