With the loss and modification of natural roosting habitat afforded by caves, abandoned mines have assumed increased importance as alternative roosting sites for Townsend's big-eared bats (Corynorhinus townsendii). However, increased human safety concerns have led to accelerated abandoned mine closure programs. To protect roosting sites in mines with significant bat activity, bat-compatible gates are installed that allow continued access to mine workings. Aside from ensuring public safety, these gates provide protection from disturbance to roosting bats. We evaluated the effects of gating on bat flight behavior at maternity colonies in 2 previously gated (control) and 2 ungated (treatment) mines that were gated during this study. We used an infrared video camera to record bat flight behavior at the entrances to each of the 4 study mines for 2 consecutive mornings and a single night each month during the warm season. Entrance (03:00–06:00) and emergence (21:00–24:00) surveys comprised 3 consecutive hours. Overall circling activity increased more than 6-fold at openings of treatment mines following gating (P < 0.001). Crowding during emergence was significantly higher (P = 0.023) in newly gated mines than in previously gated mines. Gates affect subadults during the initial-volancy periods, as detected through collisions with the gates. Increased activity of bats and collisions with the gate, which result in bats falling to the ground at mine openings, may amplify vulnerability to predators and increase energetic demands.