The effects of competition regulations on innovation are, in theory, ambiguous. Using a panel of twenty-five OECD countries over 1995–2015, we estimated how domestic and foreign competition affects innovation. Reducing regulation intensifies domestic and foreign competition, increasing R&D expenditure and patenting. Accounting for interaction between these two sources of product market competition, we find that domestic regulation directly led to growing R&D expenditure and patent production, whereas competition from foreign regulation influences innovation toward its effect on domestic competition.