Objective Various organs are known to be affected by the comorbidities of acromegaly. However, the involvement of renal structural comorbidities, such as cysts, has so far remained largely unknown. In this single-center study, we aimed to determine the prevalence and factors associated with simple renal cysts in Japanese patients with acromegaly. Methods A total of 71 consecutive patients with acromegaly were analyzed, who all underwent abdominal ultrasonography at diagnosis between 1986 and 2012 at Kobe University Hospital. Results Of these 71 patients, 23 (32.4%) exhibited simple renal cysts. Acromegalic patients with renal cysts tended to be significantly older, had a higher prevalence of smoking- and higher nadir growth hormone (GH) levels during the oral glucose tolerance test (OGTT) than did those without renal cysts. A multivariate logistic regression analysis showed age, smoking, and nadir GH to be independent factors associated with renal cysts. Interestingly, the number of renal cysts positively correlated with both the basal GH levels and nadir GH levels during OGTT (r=0.66, p<0.05 and r=0.70, p<0.05, respectively). In addition, the mean diameter of renal cysts positively correlated with the systolic blood pressure (r=0.84, p<0.005). Conclusion This is the first report to show the prevalence of simple renal cysts in patients with acromegaly. Elevated nadir GH levels during OGTT were found to be associated with an increased risk of simple renal cysts. Therefore, an excessive secretion of GH may be related to the development of renal cysts.