The production planning in shipyards is complex due to the large number of ships being constructed simultaneously, the diversity of work organization and the workers’ capabilities. This study addresses the problem of assigning blocks to different in-house subcontractors in the blasting operations, one of the various processes in the shipyard. The approach takes into account the production capacity of each subcontractor, the difficulty level of the blocks, and whether the blocks can be arranged in the work area to determine the final allocation. The methodology developed utilizes a genetic algorithm, which facilitates the extension of the objective function and constraints, and allows decision-making by reflecting the appropriate weights on the objective function based on the production situation. The proposed methodology was validated through a comparison with manual planning based on actual data from the shipyard’s blasting operations.