This paper investigates Assembly Line Worker Assignment and Balancing Problem (ALWABP), focusing specifically on productive workload differences due to age and gender of workers, to minimize the number of workstations. Most of the published papers on assembly line balancing problems (ALBP) are focused only on the task processing times. However, this may cause an overload in work assignments for certain workers. A work-overload may cause fatigue and thus lead to a decrease in line efficiency and factory productivity, and also result in an increase in quality problems and work-related injuries. To avoid the negative implications of work-overload conditions, this paper assigns tasks among workstations without exceeding the cycle time or the age and gender-adjusted physical workload capacity (PWLC). We propose a regression model to determine age and gender-based PWLC. Six different age categories are analyzed to show the impacts of age and gender on PWLC. We propose a binary (0-1) integer linear programming (BILP) for ALWABP, where age and gender-adjusted PWLC is considered. The efficiency of the model is shown on test problems and a real-life application in a textile firm. An ALWABP is considered taking into account the processing times and physical workloads for a textile factory assembly line of 53 tasks. The numbers of stations for ALWABP without and with the physical workload in the textile firm assembly line case are 5 and 6, respectively. All workstations are balanced in terms of physical workload and processing times. The results show that advancing average age increases the number of stations (NS), and this situation triggers a reduction in line efficiency (LE) and PWLC utilization ratio.