Equine-Assisted Services (EAS) offer significant benefits for individuals with intellectual and/or physical disabilities. However, ensuring the welfare of the horses involved remains a key ethical concern. The objective of this study was to assess the affective states of horses involved in EAS while also establishing behavioural thresholds for indicators of positive or negative affective states. A total of 98 horses were observed over a two-month period, accumulating data about horse behaviour and session characteristics from 830 EAS sessions. Horses participating in coaching programs averaged four sessions in two months
those involved in therapeutic riding averaged 31 sessions. Equine behaviour and field experts defined behavioural thresholds to assess welfare standards. Negative state behaviours were predominantly aligned within excellent or neutral thresholds, while positive state behaviours were observed from unacceptable to excellent. Principal Component Analysis (PCA) of the gathered behavioural data identified six affective states in coaching sessions and four in therapeutic riding, explaining 63% and 73% of the total variation, respectively. Among these states, "comfortable" was the most frequently observed. Multiple linear regression showed several significant variables, highlighting the importance of health, suitable horse selection, and proper management in promoting positive affective states in EAS.