Background: There is a return of colistin as the treatment of last resort for multi-resistant bacteria. However, due to the limited penetration in the lung parenchyma and the renal side effects, the effectiveness of intravenous (IV) colistin therapy has been questioned. Colistin inhalation therapy is deemed tolerable, safe, and could be a beneficial therapy. However, the efficacy and safety of colistin monotherapy is still unclear. Therefore, this study aimed to describe the use of inhaled colistin in patients with drug-resistant bacterial pneumonia at a tertiary hospital in Vietnam from July 2021 to September 2022. Methods: A descriptive retrospective study was conducted using medical records of all inpatients who were treated with inhaled colistin at a tertiary hospital in Vietnam, from July 2021 to September 2022. Results: This study included 12 hospital pneumonia patients, aged 81.5±13.5, equivalent to 21 inhaled colistin treatment courses. The disease mainly causes Acinetobacter baumannii (100%), Klebsiella pneumonia (47.62%), and Pseudomonas aeruginosa (38.09%). 100% of patients were taken an aerosol colistin dose of 4 million IU every 8h of aerosol for 30 minutes from 7 to 14 days. The success of clinical efficacy was 95.23% while the success of microbiological efficacy was just 42.86%. 5/12 patients have recurrent infection, and 1 patient used 6 courses of aerosol colistin treatment in 1 hospitalization. Changes in kidney function before and after the use of colistin aerosol are negligible. Conclusion: Colistin inhalation therapy has been shown effective in treating multidrug-resistant pneumonia without causing kidney toxicity. However, the rate of recurrent infection in the study was quite high, so a prospective study with a larger sample size should be conducted to further evaluate the efficacy and toxicity of inhaled colistin therapy.