Background: Absolute monocyte count (AMC) correlates with survival outcomes in various hematologic malignancies. However, its role in myeloid malignancies including AML needs to be highlighted. So, this prospective cohort study aimed to assess the effect of AMC on the treatment outcome and survival in a 56 adult de novo AML patients with monocytic differentiation, admitted to the Clinical Hematology Unit, Internal Medicine Department, in a tertiary referral hospital in Egypt, from July 2016 to June 2019. Results: The initial AMC was measured either by manual differential or the hematology automatic analyzer Sysmex XN-2000 and patients were classified by using receiver operating characteristic curve into two groups monocytopenic (≤ 4 × 109/L) and non-monocytopenic (> 4 × 109/L) group; including 24 (42.9%) and 32 (57.1%) patients, respectively. After a median follow up period of 7.7 (range 0.5–33.2) months, the monocytopenic group was associated with a significantly higher CR rate (P = 0.019), with a lower death as well as relapse and early relapse rates (P = 0.011, 0.033, and 0.002, respectively). Moreover, low initial AMC along with intensive induction were independently associated with complete response to induction chemotherapy with HR, 5.04 [1.37–18.58], P = 0.015, and 5.67 [1.48–21.71], P = 0.011, respectively by using the multivariate logistic regression model. Regarding survival, the monocytopenic group was associated with a better 3-year disease-free survival rate (P = 0.011) in univariate Cox regression only but did not reach significance in the multivariate model and did not affect the overall survival as well. Conclusion: Initial AMC was found to be an independent prognostic immune biomarker for treatment response in AML patients with monocytic differentiation. However, it did not appear as an independent predictor of survival in a multivariate analysis. Keywords: Acute myeloid leukemia, Monocytic differentiation, Immune biomarker, Response, Absolute monocyte count