Background Undiagnosed hypertension is defined as individuals who were hypertensive but did not report having been told by a health professional that they have hypertension. It is an important risk factor for development of chronic kidney disease, cardiovascular disease and all-cause mortality. Despite those problems and benefits of finding individuals with undiagnosed hypertension to prevent its outcomes, no enough investigations have been done regarding the prevalence and associated factors of undiagnosed hypertension. Therefore, the objective of this study was to assess the prevalence of undiagnosed hypertension and its associated factors among bank workers in Ethiopia. Methods An institutional based cross-sectional study was held at Bahir Dar city bank workers. The simple random sampling technique was used to select the study participants. Self-administered structured questionnaire and physical measurement were used to collect data. The data were entered into EPI data 3.1 versions and exported to SPSS version 23.0 statistical software for further analysis. In order to decide the association between independent and dependent variables; multivariate logistic regression analysis was implemented. A P-value of < 0.05 was used as the criterion for statistical significance and OR with 95% confidence interval was used to indicate the strength of association. Result In this study from a total of 524 participants 513 were completed the questionnaire correctly, which gives a response rate of 97.9%. The overall prevalence of undiagnosed hypertension among bank workers was 24.8% with (95% CI 21.1–28.5). Multivariate logistic regression revealed that age 35–44 [AOR = 2.56, 95% CI: (1.60–4.09)], being male [AOR = 3.61, 95% CI: (1.84–7.05)], having moderate knowledge [AOR = 3.81, 95% CI: (2.29–6.34)], having poor knowledge [AOR = 6.19, 95% CI: (3.07-)12.48], and being physically inactivity [AOR = 2.91, 95% CI: (1.26–6.76)] were variables significantly associated with undiagnosed hypertension. Conclusion The prevalence of undiagnosed hypertension among bank workers in Bahir Dar city was found to be high. An age group of 35–44 years, being male, having moderate and poor knowledge and being physically inactivity was the variables that were significantly associated with undiagnosed hypertension. Therefore, creating awareness, frequent screening and implementation of an appropriate intervention for this vulnerable group is important.