Background: Adrenocortical tumors (ACTs) are detected in 5–7% of the general population. Dysregulation of micro-ribonucleic acid (microRNA) biogenesis machinery- is involved in a variety of human cancers. Dicer1 is an essential component of microRNA machinery. Aim: To evaluate the diagnostic and prognostic significance of Dicer1 in adrenocortical adenoma (ACA) and carcinoma (ACC), then correlate the results with clinico-pathological data. Material and Methods: Forty adrenocortical lesions were included in this retrospective study, included (20) ACA and (20) ACC. Clinicopathological characteristics of examined cases were correlated with the IHC expression of Dicer1. Results: Dicer1 IHC expression was more frequent in ACC (65%) than in ACA (25%), (P =0.04). But among ACC, a weak Dicer1 expression was significantly more frequent in advanced ACCs. There was a significant statistical inverse relation between Dicer1 expression in studied ACC cases according to tumor size, weight, Weiss score, lymph node metastasis, lympho-vascular invasion and ENSAT stage (P 0.05). Dicer1 showed 76% sensitivity and 67% specificity for differentiating ACA from ACC. Conclusion: Reduced Dicer1 expression with tumor progression in ACC may play a role in the tumorigenesis and fu