Problematic dog behaviors at animal shelters may stop animals from being adopted and may lead to euthanasia. Current dog behavior assessments lack scientific validity and do not identify the function (i.e., the reinforcement driving the behavior) of problem behavior. Functional analysis (FA) is an empirical method for determining the functions of problem behavior by manipulating antecedent and consequent events. By determining the functions of problem behavior, function-based treatments can be developed to reduce problem behavior and increase appropriate behavior. Although FAs have been shown to be effective at identifying the functions of problem behavior in humans, there are few published articles that determine the effectiveness of FA methodology in identifying the functions of problem behavior in nonhumans. The purpose of the present study was to analyze the effectiveness and social validity of a modified FA in determining the maintaining function of inappropriate behaviors of animal shelter dogs. The results of the FAs were verified through function-based treatments.