A dual resource constrained (DRC) with fewer operators who could control parallel semi-automatic simultaneously potentially faces the unbalance workload problem that is related to social topics in Global Reporting Initiative Sustainability Reporting Standards (GRI Standards). Balancing the operator workload, on the other hand, could change the schedule structure resulting in some additional delay. This proposed study develops a multi-objective mixed integer non-linear programming (MINLP) with total tardiness and workload smoothness index (WSI) as the objective functions to measure the delay and workload balance respectively. To solve the model, a well-known non-dominated sorting genetic algorithm II (NSGA-II) is used to yield the non-dominated solutions showing the alternative schedule options. The results show that the effort in balancing the workload could raise the lateness. The important finding is that WSI can be improved significantly in the small proportion on the most left side of the total tardiness range.