The purpose of this thesis is to describe effectiveness of animal-assisted therapy with various populations. Animal-assisted therapy can be defined as “any intervention that intentionally includes or intentionally incorporates animals as part of the therapeutic or ameliorative process or milieu.” The profession of social work has been compelled to investigate the use of animal-assisted therapy to supplement treatment in order to provide best practices available to clients. Families, veterans, children, individuals with mental health diagnoses, elderly and prisoners are all populations that have been proven to benefit from animal-assisted therapy. The specific uses of animal-assisted therapy in treatment interventions will be explored in detail. Benefits that these groups have gained from the use of the intervention include the positive impact on the therapeutic alliance, reduction of anxiety, depression and social isolation. Limitations and implications for use of animal assisted therapy within the social work profession will be provided.