Drosha initiates the production of miRNAs from precursors. To study the functions of miRNA in adrenal steroid production, we knocked down Drosha expression in the HAC15 cell, a subclone of the H295R human adrenocortical cell, using lentiviral vectors to deliver shRNA of Drosha. Drosha protein levels in the infected HAC15 cells were reduced by 74.3% compared to empty vector infected control cells. Drosha knock‐down led to 36.3% and 46.4% suppression of aldosterone production under basal and after angiotensin II (A‐II) stimulated conditions, respectively. Basal and A‐II stimulated StAR and HSD3B2 mRNA expression levels in the Drosha knock‐down cells were also significantly suppressed; expression of other enzymes required for aldosterone synthesis were not altered. In conclusion, suppression of Drosha significantly diminished basal and A‐II stimulated StAR and HSD3B2 mRNA expression and aldosterone production, suggesting that at least one miRNA is essential for aldosterone production.Support: VA Medical Research Funds, NIH HL27255 & HL75321