Loss of roosting habitat is widely understood as one of the major causes of declining bat populations worldwide. While some species of bats have adapted to the use of anthropogenic structures (e.g., bridges and culverts) for roosting, this behavior also renders these bat colonies vulnerable during structure widening, seismic retrofit, maintenance, and replacement projects. Efforts made to minimize and mitigate impacts to bats are not always successful because many biologists and environmental planners developing mitigation are not knowledgeable about the natural history or ecology of bats or how to provide appropriate mitigation, there is little published literature available on successful mitigation strategies, and because “one size fits all” mitigation measures are not applicable to bat roosts. After designing and implementing dozens of successful mitigation projects for bats in Southern California, we have developed an informal protocol for creating effective mitigation strategies for transportation projects involving bat roosts. This presentation discusses examples of ways in which mitigation for bats can fail and how to avoid the most common pitfalls. This presentation also proposes a systematic, stepwise approach that can be used for a variety of transportation infrastructure and even other types of projects to minimize and mitigate potential impacts to bats.