The optimality of supply chain networks (SCN), associated with inventory management, is one of the mandatory objectives for industries.  The main purpose of this research is to minimize the total expected costs of collaborative supply chain networks. This research investigates the applicability of the modified firefly algorithm for minimizing the total cost of collaborative supply chain networks based on large-sized problems, in which the vendor uses VMI policy for collaborations and direct-delivery policy for non-collaborations.  It is assumed that industrial plants with assigned warehouses are willing to share their existing capacities with other industrial plants with no assigned warehouses to reduce the undesirable costs associated with shortage and extra inventory.  Since this problem is one of the larger problems related to industrial supply chain networks, commercial software cannot obtain the optimal results for these problems considered in this research.  To achieve better findings, we applied a modified firefly algorithm to solve the problem.  The computational time of the proposed algorithm was also reduced as compared with commercial software and standard firefly algorithm.