We develop a dynamic model to investigate the effects of environmental corporate social responsibility (ECSR) on a monopolist's investments in green product and process innovation. We find that ECSR increases the steady‐state investments of green product and process innovation only when the weight a firm gives to pollution is large, while ECSR does not affect the complementarity (substitutability) relationship between green product and process innovation in the long run. To achieve a socially optimal investment in green product innovation, the government should urge the firm to pay more attention to the environment than to the consumer surplus.