Abstract: Objective: To evaluate the efficacy, prognosis, and safety of venetoclax combined with hypomethylating drugs in patients with untreated acute myeloid leukemia (AML) who were not suitable for intensive therapy and in patients with relapsed/refractory AML (R/R AML). Methods: A retrospective analysis was performed for 87 patients with AML who were treated with venetoclax combined with hypomethylating agents at Qilu Hospital of Shandong University from July 2020 to October 2022. They were assigned into the untreated unfit group and the relapsed/refractory group. The clinical data of the patients were collected, and the efficacy, survival and adverse events were analyzed. Results: Efficacy evaluation: The median course for the untreated unfit group was 3 (range: 1–14), and the proportions of patients achieving complete response (CR), CR/CR with incomplete hematologic recovery (CR/CRi), overall response rate (ORR), and measurable residual disease (MRD) negative rate was 42.86%, 77.55%, 83.67% and 34.69%, respectively. The median course for the relapsed/refractory group was 2 (range: 1–10), and the proportion of patients achieving CR, CR/CRi, ORR and MRD negative was 23.68%, 52.63%, 60.53% and 31.58%, respectively. The correlation analysis between genotype and efficacy showed that patients with isocitrate dehydrogenase (IDH) mutations had a higher CR/CRi rate and MRD negative rate as compared to patients with IDH wild type. Survival analysis: The median follow-up time of the untreated unfit group was 14 months, the median survival time was not reached, and the one year cumulative survival rate was 64.6%. The median follow-up time of the relapsed/refractory group was 8 months, the median survival time was 9 months, and the one year cumulative survival rate was 46.7%. Safety evaluation: The incidence of hematological and non-hematological adverse events was 100.00% and 97.70%, respectively. Furthermore, tumor lysis syndrome (TLS) occurred in 2.3% patients. Conclusions: Venetoclax combined with hypomethylating drugs is effective in patients with untreated unfit AML and R/R AML. Almost all the patients experience adverse events; however, they are tolerable for most patients. Monitoring for TLS should be strengthened during treatment.