Herein we describe a safe, practical, and inexpensive device for restraining bats (Order Chiroptera). With advances in molecular techniques, biopsies from the flight membranes of bats have become routine; however, tissue sampling requires that the bat be restrained and often this work is performed by two people: one to hold the animal and another to conduct the procedure. The McMaster bat restrainer permits a single user to safely, effectively, and comfortably restrain a bat — both in the field and in the laboratory — while still having full access to its forearms, flight membranes, and/or dorsum/ventrum. The restrainer is light weight, portable, simple to use, easy to modify, and minimizes handling stress on bats. Investigators should take precautions to appropriately decontaminate the restrainer when working in areas where bats could be infected with the psychrophilic fungus that causes white nose syndrome (WNS), Pseudogymnoascus destructans.