The cotton bollworm, Helicoverpa armigera, is one of the most important agricultural pests of many economic crops worldwide. Herein, we found a novel single-strand RNA virus by RNA-Seq and Polymerase Chain Reaction (PCR) method in H. armigera named Helicoverpa armigera iflavirus (HaIV), which possessed a genome with 10,017 nucleotides in length and contained a single large open reading frame (ORF) encoding a putative polyprotein of 3021 amino acids with a predicted molecular mass of 344.16 kDa and a theoretical isoelectric point (pI) of 6.45. The deduced amino acid sequence showed highest similarity (61.0%) with the protein of Lymantria dispar Iflavirus 1. Phylogenetic analysis with putative RdRp amino acid sequences indicated that the virus clustered with members of the genus Iflavirus. The virus was mainly distributed in the fat body of its host and was found to be capable of both horizontal and vertical transmission. The efficiency of perorally horizontal transmission was dose dependent (100% infection rate with a viral dose of 108 copies/μl) while vertical transmission efficiency was found to be relatively low (<28.57%). These results suggest that we have found a novel member of genus Iflavirus in H. armigera.