In this quality improvement study, data from the Creditor Reporting System were used to estimate flows of total DAAH and per-adolescent DAAH and to assess its distribution by donors, regions, and countries and the leading causes of burden of disease (ie, disability-adjusted life-years) in 132 developing countries between January 1, 2003, and December 31, 2015. Through use of a key word search and various funding allocation methods, 2 sets of estimates were produced: adolescent-targeted DAAH that included disbursements to projects with a primary adolescent health target and adolescent-inclusive DAAH that included disbursements to projects with either a primary or partial adolescent health target, as well as projects that could benefit adolescent health but did not include age-related key words.