We consider a supply chain where manufacturers can be differentiated along two dimensions—product quality and cost of social responsibility effort. There are two types of manufacturers: high and low. Under complete information, high-type manufacturers exert a greater level of social responsibility effort in comparison with the low-type manufacturers. We then show that under incomplete information, high-type manufacturers have an incentive to exert an even greater level of social responsibility effort. Surprisingly, the extent of effort put in by high-type firms cannot be lower and, in some cases, can be strictly higher under incomplete information.