Recycled content products play an important role in sustainable development through a significant reduction in natural resource use, energy consumption as well as much less greenhouse gas emissions. These products are made from a mix of virgin and recycled materials with specific proportions known as recycled content levels. To the best of the author’s knowledge, the lot-sizing and replenishment policy of these products has not yet been studied. Motivated by this research concern, this thesis considers a five-echelon closed-loop supply chain (CLSC) of these products consisting of a manufacturer, a retailer, a supplier, a material recovery facility (MRF), and a recycling facility. In this supply chain, the supplier and the recycling facility respectively provide the virgin and recycled raw materials to the manufacturer. The manufacturer mixes them based on the recycled content level to produce and ship the ?nished products to the retailer. The recycling facility recovers the manufacturer’s production waste as well as the returned used products collected by the MRF. We aim at maximizing the chain-wide profit by optimizing the shipments among the supply chain parties from a joint economic lot-sizing (JELS) point of view. Mathematical models are developed as mixed-integer non-linear programming. We propose a Branch-and-Bound algorithm, which provides the optimal solution, and a fast heuristic procedure, which has given the optimal solution in 96% of all tested instances. Numerical results indicate the JELS policy increases the total profit of the whole supply chain, while it may decrease the profit of some parties. To coordinate the CLSC, two successful and valid models called disproportionate profit-sharing (DPS) and proportional profit-sharing (PPS) are presented that operate under quantity discount contracts. The DPS guarantees each player gains more or equal profit in the JELS than the independent decision-making structure. However, the PPS ensures equitable increases in the own profits accruing to all players from the JELS. Based on the results of this research, it is recommended to managers and decision-makers to use DPS method in vertically integrated CLSCs and decentralized ones with dominant player(s), and PPS method in decentralized ones with no dominant players. Next, it is proved for the recycled content level that one of the two extreme (bang-bang) strategies, i.e. either its upper or lower bounds, is the best level, while the stationary point within the range can be optimal under certain limited conditions. Moreover, sensitivity analysis indicates that a decrease in manufacturing scrap fraction reduces the number of shipments to each party. It increases the profits of the manufacturer, the MRF, and the whole supply chain, which it decreases the profits of the supplier and the recycling facility, and has a negligible effect on the profit of the retailer. It also indicates that retail price, unit production cost, extraction cost per unit virgin material, and demand rate play the most influential effect on the optimal total profit that should be given special attention by industry managers.