RNA interference (RNAi) is a conserved mechanism that catalyzes sequence-specific gene silencing and has been used for loss-of-function genetic screens in many organisms. Here, we demonstrated that the expression of Caenorhabditis elegans SID-1 (CeSID-1) could trigger effective gene silencing in the cultured silkworm cell line, BmN4 (BmN4-SID1). Soaking the BmN4-SID1 in dsRNA corresponding to endogenous target genes induced a significant decrease of the amount of mRNA or protein. A small amount of dsRNA was enough to silence the target gene in a few days. Overexpression of CeSID-1 did not affect the cell viability. Our results suggest that BmN4-SID1 can be used in many applications in silkworm cells and will become a valuable resource for gene analysis.