Introduction Dental caries is a major public health problem. In Ethiopia, prevention and treatment of oral health-related illness had given little attention and there is limited data on the extent and factors associated with oral health-related illnesses and oral care practices. Objective This study was aimed to investigate the prevalence of dental caries and associated factors among patients visiting Shashamane Comprehensive Specialized Hospital (SCSH). Methods A hospital-based cross-sectional study was conducted among 288 patients who visited SCSH dental clinic from March 1, 2021, to April 15, 2021. A questionnaire was employed to collect the background characteristics of the participants. Dental caries was confirmed as per World Health Organization guidelines. Data were analyzed using SPSS version 24. Bivariable and multivariable logistic regression were used to determine predictors of dental caries. A p-value less than 0.05 was taken as a cut point to determine a significant association. Results The overall prevalence of dental caries was 64.6% with 95% CI (58.8‒70.1). The mean of Decayed, Missing, and Filled Teeth was 1.33. Dental caries was significantly higher among respondents who did not brush their teeth (AOR = 3.589, 95% CI:1.756‒7.334), who consumed sugary food (AOR = 3.650, 95% CI: 1.747‒7.628), those with monthly a income of less than 5000.00 Ethiopian Birr (AOR = 2.452, 95% CI (1.193‒5.042), and those who had poor oral hygiene status (AOR = 1.826, 95% CI: 0.901‒3.700). Conclusions This study revealed a high prevalence of dental caries among patients visiting the dental clinic. Tooth brushing habits, consumption of sugary food, and poor oral hygiene were significantly associated with dental caries.