Supply Chain Management (SCM) is an area that has recently received a great deal of attention in the business community. SCM is the management of material and information flows both in and between facilities, such as vendors, manufacturing and assembly plants and distribution centers. Effective coordination plays an important role in the successful operation of supply chain. If no such coordination exists in the chain then the vendor and the buyer will act independently to make decisions that maximize their respective profits or minimize their costs. This may not be optimal if one considers the supply chain as a whole. In this study, we focus on optimally determining lot-sizing policies for a deteriorating item among all the partners in a supply chain system with a single-vendor and multiple-buyers so as to minimize the average total costs. In this regard, in literature, a coordinated single-vendor multi-buyer supply chain model by synchronizing delivery and production cycles has been proposed. The synchronization is achieved by scheduling the actual delivery days of the buyers and coordinating them with the vendor’s production cycle. We extend this model for deteriorating items that occurs for most products in the real world. A mathematical model for our proposed coordination is developed and analyzed. The results of the numerical examples show that the synchronized cycles policy works better than independent optimization as well as restricting buyers to adopt a common order cycle.