We find that firms’ tax planning exhibits strategic reactions: firms respond to changes in their industry-competitors’ tax planning by changing their own tax planning in the same direction. We document evidence of these strategic reactions in two distinct research settings that entail an exogenous increase and decrease in competitors’ tax planning. We also find evidence that strategic reactions stem from concerns about appearing more tax aggressive than industry competitors, some evidence that they stem from firms learning from the tax planning of their industry competitors, and no consistent evidence that they stem from leader-follower dynamics.