More and more contract manufacturers have started to establish their own brands besides providing manufacturing service for retailers who operate exclusive well-known brands. This paper studies the encroachment strategy of a contract manufacturer in a supply chain and the impact of fairness concern. Four scenarios are investigated by building game models: no fairness concern, the retailer’s fairness concern, the contract manufacturer’s fairness concern, and both members’ fairness concern. The results show that when there is no fairness concern, the contract manufacturer always has motivation to encroach. However, when there exists fairness concern, only when the reservation price is sufficiently high, the contract manufacturer will encroach. Fairness concern has certain strength to stop the contract manufacturer’s encroachment. When the reservation price is sufficiently low, the encroachment of the contract manufacturer benefits the retailer, or else it will harm the benefit of the retailer. The effect of fairness concern on profit margin and wholesale price decisions is opposite under different encroachment strategies. However, the fairness concern has no impact on the retail price of the private brand. Under encroachment strategy, contract manufacturer’s or both members’ fairness concerns have positive effect on the retailer’s profit in certain conditions. However, the fairness concern always decreases the contract manufacturer’s profit no matter what the form it is. Numerical examples show that it is best for the supply chain that both members have fairness concern under no encroachment. However, when the contract manufacturer has a private brand, it is best for the supply chain that no one has fairness concern when the advantageous inequity concern parameter is sufficiently low. When the advantageous inequity concern parameter is sufficiently high, it is best for the supply chain that both members have fairness concern.