This paper explores the phenomenon of trademark squatting – a situation in which someone other than the original brand owner obtains a trademark on a brand. We develop a model that shows how squatting results from market uncertainty that leads brand owners to rationally forgo registering trademarks, creating opportunities for squatting. We create an algorithm to identify squatters in the Chilean trademark register and show empirically that squatting is a persistent and systematic phenomenon. Using data on trademark oppositions, we show that squatting leads brand owners that have been exposed to squatting to ‘over-protect’ their brands by registering disproportionately many trademarks and covering classes other than those directly related to their products and services. Trademark squatting, therefore, creates a strategic, albeit excessive, response by brand owners which inflates trademark filings.