Introduction: Hypertension is a non-communicable disease which is a global health problem. It is the leading cause of premature death. Most people with HTN are asymptomatic and go undiagnosed for years. Undiagnosed hypertension is defined as individuals who were hypertensive but did not report having been told by a health professional that they had hypertension. It is an important risk factor for development of cardiovascular disease, chronic kidney disease, and all cause mortality. Objective: The aim of this study was to determine the prevalence and associated factors of undiagnosed hypertension among attendants of Tibebe Ghion specialized hospital, Bahir Dar, North-West Ethiopia, 2022. Methods: An institutional based cross-sectional study was held from August 15-September 15 2022. Socio-demographic and behavioral characteristics of the participants were collected using interviewer-administered semi-structured questionnaires. Physical measurements including body mass index, waist circumference, and blood pressure were collected using standardized measuring instruments. Statistical analysis was collected using SPSS version 25 software. Univariate logistic regression model was used to present the results. The p value less than 0.05 in a multivariable analysis was considered statistically significant at 95% confidence interval Result: From a total of 191 participants, 105 (55%) males and 86 (45%) females with a mean age of 37.14±12.51years. The prevalence of undiagnosed hypertension among adults was 25.1%. Of these, 16.2% were males and 8.9% were females. Factors including age (above 50years) (AOR=2.89, 95% confidence interval (0.95, 8.82), p=0.02), male sex (AOR=3.89, 95% confidence interval (1.05, 14.52), p=0.04), unemployment (AOR=3.31, 95% confidence interval (0.88, 12.47), p=0.04) were significantly associated with undiagnosed hypertension. Conclusion: The prevalence of undiagnosed hypertension among adults was found to be remarkable. Therefore, intervention measures should be performed at the community level; particular emphasis should be placed on prevention by introducing lifestyle modifications and creating awareness about the problem so that early detection and intervention is possible. Key words Undiagnosed Hypertension, Attendants, Tibebe Ghion specialized hospital, Risk factors