Respiratory syncytial virus (RSV) is a major cause of acute lower respiratory infections in infants and susceptible adults. Although the epidemiology and immunobiology of the virus have been widely investigated, no safe vaccine has yet been approved, and treatment with the antiviral ribavirin is limited to severe cases. Nonetheless, new antiviral agents are undergoing development1 . A new approach encompasses influenza A virus (IAV) defective interfering particles (DIPs). IAV DIPs have been proposed as an antiviral treatment against interferon (IFN)-sensitive respiratory viruses such as influenza A and B, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and yellow fever virus (YFV). In this study, we established a method for RSV production and assessed the virus’ replication dynamics. Moreover, the inhibitory potential of IAV DIPs against RSV propagation was studied in in vitro coinfection experiments. Specifically, we investigated the antiviral activity of DI244, a prototypic, wellcharacterized DIP that harbors a large internal deletion in Segment 1 of the viral genome, and of OP7, a newly discovered DIP that presents 37 point mutations on Segment 7 of the viral RNA (vRNA)2,3 . We report that DI244 and especially OP7 are able to partially suppress RSV replication in IFN-competent cells. Furthermore, we show that the inhibitory potential of IAV DIPs is dependent on the innate immune response stimulation. It appears that DI vRNAs were recognized by the retinoic acid inducible gene I (RIG-I), leading to upregulation of type I and type III interferons (IFNs). IFNs activated the janus kinase-signal transducers and activators of transcription (JAK/STAT) signaling cascade, which culminated in the expression of interferon stimulated genes (ISGs). Our results suggest that the IAV DIPs DI244 and OP7 may represent a promising antiviral agent for the treatment and prophylaxis of RSV infection.