Biofilms are formed by microorganisms that grow in aggregate, usually attached to biotic and abiotic surfaces, forming a sessile community embedded in a self-produced extracellular polymeric matrix. Biofilm-producing microorganisms, such as Acinetobacter baumannii, acquire greater resistance to the action of physical and chemical agents, which may contribute to the prevalence of these pathogens in industrial environments. The exposure time, as well as the concentration of the disinfectant used, are important factors for the effective elimination of contaminants and must be evaluated. This study aimed to evaluate the biofilm tolerance against disinfectants formed by A. baumannii strains B653/16, B676/17, and B713/17 isolated in a pharmaceutical industry. Biofilm formation assay was performed in 2.0 cm diameter stainless-steel discs. Disinfectants tested included: alcohol 70%/15min, sodium hypochlorite 0.1 and 0.5%/15min, and quaternary ammonium 0.05 and 0.08%/20min. After biofilm formation and treatment, samples were washed and fixed. Afterwards, samples were dehydrated in crescent series of acetone. Ultrathin sections were stained and observed using a transmission electron microscope. Exposure to alcohol and quaternary ammonium, in both concentrations, reduced the biofilm of B646/17 and B713/17 strains but not of B653/16. Sodium hypochlorite at 0.1 and 0.5% were able to drastically reduce the biofilm of all the strains. Sodium hypochlorite at ≥0.1 %/15 min was the most effective disinfectant for A. baumannii biofilm elimination. As sodium hypochlorite cannot be applied on certain surfaces due to its corrosive action, other studies are necessary to find alternative disinfection procedures to eliminate A. baumannii biofilms in stainless-steel surfaces. Scanning electron microscopy seems to be an efficient technique that can be applied for biofilm evaluation. It can be used as part of the contamination control strategy of the pharmaceutical facility to develop preventive and corrective measures to eliminate microbial biofilms in stainless-steel surfaces.