Ensuring the well-being of horses participating in therapies such as psychotherapy, occupational therapy (OT), physical therapy (PT), and speech-language pathology (SLP) is critical to keeping the clients, horses, and practitioners safe and maximizing session efficacy. Welfare assessment and steps to increase horse well-being are needed as the public becomes more aware of and invested in conversations regarding animal welfare. This chapter presents an overview of the Five Freedoms and the Five Domains, broad models for welfare assessment. Specific measures used in assessing welfare and stress in horses in equine-assisted services and their physiological underpinnings are then discussed. An overview of the literature on the well-being, stress, and welfare of horses participating in therapies integrating horses is presented, along with a short discussion of what conclusions can be drawn from this literature base. The potential consequences of horse well-being for human outcomes are then considered. This chapter concludes with a short discussion of recommendations for future research and implications for practice.