A 2012 survey of upland U.S. cotton producers was analyzed to determine the factors contributing to changes in weed management costs (WMCs) after the identification of herbicide‐resistant weeds. An ordered probit regression estimated changes in WMC as a first‐order Markov process. The most important determinants of post‐resistance cost increases were initial WMCs, adoption of labor‐intensive remedial practices, and wick application of herbicides. Cultivation and mechanical/chemical‐intensive practices did not increase WMCs. Post‐resistance changes in WMC ranged between $85 and $138 ha−1, depending on the practices adopted. WMCs increased by $88 ha−1 when cost‐neutral practices were adopted. The in‐sample aggregate costs of managing herbicide resistance ranged between $25 and $53 million, depending on the types of adopted practices.