This paper investigates how corporate advocacy can produce unexpected consequences by triggering mobilization from opposing ideological interests. Recent research on corporate political ideologies suggests that ideological firms—firms whose organizational members are ideologically engaged—are the main and early participants in advocacy issues of contentious nature. However, what remains underexplored is whether and how the actions of ideological firms affect other firms in the population, especially the possibility that actions of ideological firms can be met by strong ideological opposition from their competitors, which can strategically differentiate themselves in doing so and gain competitive advantage. Using uniquely detailed records of U.S. corporate foundations’ philanthropic giving to 4,021 advocacy nonprofits from 2003 to 2015, we find strong evidence that ideological firms’ giving encourages a stronger response of giving from their ideological opponents than from their ideological allies in the issue area of their choice. We also find that such asymmetry in the response between ideological opponents and allies is moderated by firm-level, issue-level and market-level contingencies, such that the asymmetry is stronger among ideologically homogeneous firms, in issues that involve higher contention, and when firms face strong labor market competition. These results advance our understanding on the dynamics of ideological competition at play in the market of advocacy giving, and suggest that, without accounting for the structure of ideological competition, ideological firms’ advocacy actions may backfire, leading to increased conflict and polarization.