Purpose: The aim of this study was to determine the preoperative sleep quality and pain intensity of patients hospitalized in the surgical services of a university hospital, and to evaluate the relationship between sleep quality and pain intensity and the factors affecting it. Design: The study was a descriptive cross-sectional study. Methods: The study was conducted on 139 patients over the age of 18 who were hospitalized in the surgical services of Eskişehir Osmangazi University Health Practice and Research Hospital between March 1, 2019 and July 31, 2019, and agreed to participate in the study. The “Visual Analog Scale for Pain (VASP)” was used to evaluate the pain intensity of the patients, and the “Visual Analog Sleep Scale (VASS)” to determine the quality of sleep. Findings: The sleep quality of women, those who had sleep problems before hospitalization and those who had sleep problems in the preoperative period was worse (P <.001). Patients who had a companion and had sleep problems in the preoperative period had higher pain levels (P <.001 for each). As the pain levels of the patients increased, their sleep quality deteriorated (P <.001). Multiple linear regression analysis revealed that for each unit increase in the variable of having sleep problems in the preoperative period increases the VASS score by 180.422 points and the VASP score by 1.788. Being a woman increased the VASS score by 91.469 points, and the presence of a companion increased the VASP score by 1.644 points. Conclusions: The preopertive sleep quality and pain intensity of surgery patients were interrelated. Having sleep problems in the preoperative period affected both the sleep quality and pain intensity of the patients. While female gender affected the sleep quality of the patients hospitalized in surgical services, the presence of a companion was found to affect the severity of pain.