Background <p>Although dyslipidemia is commonly reported in dogs, comparative data on the magnitude of serum cholesterol disturbances have not been reported. We aimed to describe the severity of hyper- and hypocholesterolemia in dogs with common endocrinopathies and to evaluate its association with common laboratory parameters. Medical records were reviewed over a decade (2011–2022) for dogs with hypothyroidism, diabetes mellitus (DM), hyperadrenocorticism (HAC), or hypoadrenocorticism (HA), and included signalment, common laboratory and diagnostic imaging parameters, comorbidities, and medications. This retrospective study included 53 dogs with hypothyroidism, 54 with DM, 62 with HAC, and 79 with HA.</p> Results <p>Medians [range] of serum cholesterol concentration ([Chol]_s) for dogs with hypothyroidism, DM, HAC, and HA were 492 [174–1829], 321 [116–928], 309 [151–630], and 112&#xa0;mg/dL [31–309], and hypercholesterolemia was reported in 91%, 85%, 81%, and 9% for each disorder, respectively. Median [Chol]_s was significantly higher in hypothyroid dogs with a serum thyroxine concentration &lt; 0.47 (A = 607) vs. ≥0.47 ug/dL (B = 324&#xa0;mg/dL) (B-A = -299&#xa0;mg/dL; 95.21% CI of difference = [-433; -166]; <i>p</i> &lt; .0001), and significantly lower in HAC dogs with serum ALP activity &lt; 1,000 U/L (A = 275) vs. ≥1,000 (B = 360&#xa0;mg/dL) (B-A = + 74&#xa0;mg/dL; 95.14% CI of difference = [+ 25; +121], <i>p</i> = .006). Comparison among all studied endocrinopathies showed that median [Chol]_s was significantly higher in hypothyroid dogs and significantly lower in HA dogs, whereas median [Chol]_s was similar in HAC and DM dogs.</p> Conclusions <p>Serum cholesterol concentration can serve as a valuable tool to suspect certain canine endocrinopathies.</p>