Introduction: Acid base disorder is a condition characterized by alteration in blood pH by theimbalance between the components of blood leading to a life threatening situation. The main aimof this study was to find the prevalence of acid-base disorders and biochemical findings of suchdisorders in patients in a tertairy care hospital. Methods: This descriptive cross-sectional study was conducted in Nobel Medical College TeachingHospital from 1st September, 2018 to 31st August, 2019. Ethical apporoval was taken from InstitutionalReview Committee. All the patients presented to emergency department, intensive care units andwards were included during the study period. Data were entered and calculations were done inMicrosoft Excel, point estimate at 95% Confidence Interval was calculated along with frequency andproportion for binary data. Results: Out of arterial blood gas analysis of 1144 patients, the prevalence of acid base disorderswas 718 (62.76%) at 95% Confidence Interval (59.96-65.56%). Simple and mixed acid base disorderswere observed in 332 (46.24%) and 386 (53.76%) patients respectively. Respiratory alkalosis was mostcommon among 134 (40.36%) cases in simple acid base disorder whereas metabolic acidosis andrespiratory alkalosis was most common among 204 (52.85%) in mixed acid base disorder. All typesof disorders were observed more in elderly people (41-60 and >60 age group) than other age groups. Conclusions: Acid base disorder was found to be more common in very ill patients in emergency andintensive care units compared to similar studies. Mixed acid base disorder was the most commonwith male and elderly patients in predominance.