Depending on the age definition applied (e.g., chronologic, demographic, physiologic), a horse may be considered old at 15 years, 20 years, or even at an older age. The management of a horse is likely adjusted once it is considered old, however, details concerning these changes are currently sparse. Similarly, it is unclear at what age owners typically consider their horses to be old and why. To learn more about these and other topics related to older horses, a US-wide survey was conducted with owners of horses aged ≥ 15 years. The objectives of the present subsection of this survey were to 1) determine at what age horses were considered old by their owners, 2) identify the reasons for this decision, and 3) assess management changes made because the horse was considered old. The anonymous survey was distributed through social media and a press release and was online from Oct. 15th to Nov. 21st, 2020. 2717 of 2927 started surveys were eligible for analysis. Responses were received from all US states with southeastern states being most represented (38%; n = 2607). Data were analyzed descriptively with frequency counts expressed as percentages. Percentages amounted to maximally 100% for single-choice questions (s-c q.) but could exceed 100% for multiple-choice questions (m-c q.). All responses were discrete variables. At the time of the survey, about half (47.4%)of the participants considered their horse to be old (n = 2528 total responses to question; s-c q.). Most indicated to have first considered their horse old at an age of 20 (22.8%) or 25 years (14.1%) (n = 1181; s-c q.). Other ages were overall less commonly reported and hence grouped: < 15 years (1.0%), 15–19 years (24.0%), 21–24 years (22.4%), 26–30 years (13.9%), and > 30 years (1.9%). The top 3 reasons for considering their horses old were: 1) horse showed reduced ability to work/exercise (43.6%), 2) horse showed first signs of age-related disease/disorder (43.5%), 3) horse's hair turned gray/increase in gray hair (29.3%) (n = 1153; m-c q.). Ninety-one percent (90.6%) made changes to their horse's management once it was considered old (n = 1187; m-c q.). The top 3 changes were: 1) changed diet and/or supplements (65.9%), 2) exercised horse less intensely (31.3%), and 3) stopped riding/driving exercise (29.6%) (n = 1187; m-c q.). In conclusion, horses were often considered old at distinct ages (20 and 25 years), with changes in fitness level, health status, and physical characteristics (i.e., gray hair) reported as the main reasons. For almost all horses, management was adjusted once they were considered old, and changes mainly pertained to exercise regimen and diet.