Animal-assisted therapy (AAT) is used to achieve different outcomes, but recently more and more studies are conducted into its effects on mental health. Understanding the effectiveness of AAT becomes difficult not only because of the large number of cases of use, but also because of the variety of possible therapeutic animals and organizations of interaction with them. To summarize the evidence from documents on the effects of animal-assisted therapy (AAT) on mental health. A scoping review was conducted in Scopus. A total of 2294 documents were identified and 31 articles selected and included in this review. Animal-assisted therapy can have positive effects on emotional well-being, help reduce suicidal behavior and non-suicidal self-harm, anxiety and a sense of loneliness, improve mood and emotional state. Research on effects of AAT on depression and stress had mixed results, therefore, no unambiguous conclusion can be made. No significant effect on quality of life was found. This review provides a generalized assessment of the effectiveness of AAT on mental health and suggests directions of development of weaknesses in order to increase therapeutic effects. The results of this review can be useful for the professionals interested in the problem.