This paper considers the cooperation strategies in an online selling low‐carbon supply chain (OSLCSC). To promote the end‐of‐season low‐carbon product, the manufacturer in OSLCSC establishes a promotional online retailing channel based on a co‐operative agency sales format. Three possible collaboration strategies are considered. We examine the final cooperative equilibrium and find that from an environmental perspective, cooperation between the retailer and manufacturer can always promote ecological benefits. But from an economic perspective, the retailer and manufacturer will cooperate when the revenue‐sharing rate is high. In contrast, the retailer and manufacturer are always an incentive to partner with the platform. Furthermore, all the OSLCSC players could achieve a Pareto optimal in the three cooperation strategies under certain conditions. Additionally, we reveal that a high revenue‐sharing rate makes the retailer more beneficial when OSLCSC players do not cooperate. Lastly, we obtain that each cooperative strategy may be the ultimate equilibrium, depending mainly on the revenue‐sharing rate and customers' evaluation ratio of the online direct sales channel over online retailing channel.