Colistin-induced nephrotoxicity is a well-known major adverse event, which may occur within seven days [early acute kidney injury (AKI)] with a high mortality rate of 70% or after seven days (late AKI). The main objective of this retrospective study is to assess the severity and associated risk factors for the development of colistin-related nephrotoxicity. An observational retrospective cohort study was conducted over 12 months (January-December 2017). All patients with a baseline normal renal function, who received intravenous colistin for >72 h, were included. Nephrotoxicity was defined using the RIFLE criteria (Risk, Injury, Failure, Loss, and End-stage renal disease). The demographic and clinical variables were retrieved from the hospital's electronic medical record system and compiled in an electronic database. All the statistical analysis was carried out by SAS JMP from SAS Institute Inc., Cary, NC. Seventy patients met the inclusion criteria. Colistin-induced nephrotoxicity occurred in 45.71% of the patients, of whom 40.6% were at Risk, 21.9% at Injury, and 37.5% at Failure according to RIFLE criteria. In patients who developed AKI, the average total colistin dose received before AKI was 4.4 mg/kg/day. More than half of the AKI group (53.13%) received an inappropriate total dose of colistin. Age, 65 years and older, was significantly associated with a high risk of nephrotoxicity (P <0.05), which developed within 6.8 ± 0.44 days from receiving a colistin dose. Clinical pharmacy services were consulted in 28.13% of the cases, and the dose was adjusted in 37.5% of the patients. Colistin nephrotoxicity is common and is associated more with older age group and inappropriate dosing.