Multidrug-resistant (MDR) Acinetobacter is an important pathogen which has a number of virulence characters that enable them to render resistance to antibiotics thus complicating the treatment options, thereby forcing clinicians to rely on last resort antibiotic such as colistin. However, resistance to colistin has also been reported, further increasing the challenge. To detect the rate of colistin resistance and carbapenemase production among MDR Acinetobacter baumannii isolates from a tertiary care hospital in South India. This is a prospective study conducted over a period of 15 months from August 2023 to October 2024 and included 110 isolates of MDR Acinetobacter baumannii. All the isolates were subjected to colistin resistance detection using microbroth dilution method and carbapenemase production using mCIM and eCIM methods. Of the 110 isolates of MDR A. baumannii, 19 (17.27%) showed colistin resistance. The mCIM and eCIM tests showed 70 (63.63%) serine carbapenemase producers and 61 (55.45%) metallo beta-lactamase producers. This study underscores the concerning prevalence of resistance determinants among MDR A. baumannii, providing clinicians and infection control specialists with essential data to guide the formulation of effective empirical treatment strategies and infection control measures.