School-based instructional coaching is an increasingly popular approach to professional development used to support in-service learning for teachers. However, little is known about the cost of coaching. The following study aims to fill this gap. First, the study describes a framework for measuring the cost of an instructional coaching program; second, this cost framework is applied to three schools with instructional coaching programs during the 2009-10 school year. While model developers suggest a cost of $2,298 per teacher, the study found average cost per teacher at three schools to range from approximately $3,260 to $5,220. Third, a cost framework is developed and applied to three schools utilizing traditional approaches to professional development and average costs are presented for comparison. The study found that instructional coaching is between 6 to 12 times more expensive than traditional approaches to professional development. Because schools are making large investments in coaching programs, research should explore whether instructional coaching is cost-effective. By presenting a framework for measuring costs and reporting costs of a specific program, this study lays the groundwork for cost-effectiveness studies. (Contains 24 footnotes and 7 tables.) [This article was presented at the 2011 Conference of the Association for Education Finance and Policy, Seattle, Washington, on March 26, 2011.]