This study was performed to characterize the coexistence of valvar insufficiencies of the mitral, tricuspid, aortic, and pulmonary valves and their possible association with atrial fibrillation in an equine clinic population. During an 11-year period, 348 horses had been examined for cardiac arrhythmias and suspected defects of the cardiac valves at the Vetmeduni Vienna, Austria. The study population included 256 male and 92 female horses. A subpopulation of 197 (57%) horses was identified with at least one valvular disorder. In these horses, mitral valve regurgitation (MR) was reported in 124 animals (63%), aortic valve regurgitation (AR) in 101 (51%), tricuspid regurgitation (TR) in 78 (39.6%), and pulmonary regurgitation (PR) in 17 animals (8.6%). Cardiac arrhythmias were found in 130 horses (37%). The horse types that were most frequently affected by a putative valve insufficiency were the warmbloods, followed by thoroughbreds. The prevalence of insufficiencies (46%) was highest among animals between 6 and 18 years of age. There was a significant negative relationship between the occurrence of MR and AR, and AR was also significantly negatively associated with TR. Atrial fibrillation (AF) and MR coexisted most often (10 out of 38), followed by TR (8 out of 38). Although these findings were significant for the subgroup with cardiac arrhythmias, they were not significant in connection with the entire population with cardiac problems. The results of the present study showed that risk factors for being diagnosed with MR are horse type, age, and sex. MR most often occurs as an isolated defect in horses and seldom occurs in combination with AR. Additionally, MR and TR are associated with AF.