Background: This study aimed to determine the parameters associated with hemorrhagic transformation in EVT and its relationship with blood urea nitrogen to creatinine (BUN/Cr) ratio-based dehydration status. Methods: Patients’ data treated with EVT in AIS were evaluated from the years 2018 to 2023. Venous blood samples were collected prior to operation and BUN/Cr ratio was calculated. Alberta stroke program early CT (ASPECT) and collateral scores were determined. Hemorrhagic transformation was assessed by brain computed tomography. Mortality and 90-day disability rates were determined. Parameters associated with hemorrhagic transformation were evaluated according to regression analysis models. Results: There were 146 patients with a mean age of 67.01 ± 14.34 in the study. The first-pass thrombectomy rate was 32.2 % (n = 47); and 80.8 % (n = 118) of all patients achieved complete recanalization. Symptom-to-puncture and puncture-to-recanalization times were associated with hemorrhagic transformation (p = 0.004, p = 0.012). In addition, initial NIHSS (p < 0.001), number of thrombectomy passes (p < 0.001), intra-arterial thrombolysis (p = 0.008), ASPECT score (p < 0.001), collateral score (p = 0.016), and serum glucose (p = 0.047) levels were associated with hemorrhagic transformation. Decreased glomerular filtration rate (p = 0.007) was associated with symptomatic hemorrhagic transformation. Multivariate regression analysis revealed that the major parameters for hemorrhagic transformation were initial NIHSS and number of thrombectomy passes (p = 0.035, p = 0.046). No relationship was observed between BUN/Cr ratio and hemorrhagic transformation (p = 0.910). Conclusion: In this study, no relationship was detected between BUN/Cr ratio-based dehydration and hemorrhagic transformation in AIS patients treated with EVT. The main predictive factors for hemorrhagic transformation are high initial NIHSS and number of thrombectomy passes.