Paramyxoviridae have evolved various mechanisms to block IFNa/b response, in particular signaling downstream IFNAR1/ IFNAR2c receptor [20, 33] . Although members of Pneumovirinae subfamily have specific genes to encode inhibitors of IFN-a/b signaling pathway, those expressed by other Paramyxoviridae (i.e. Paramyxovirinae subfamily) are encoded by overlapping reading frames embedded within the gene P. Rubulaviruses express V proteins that target STAT1 and/or STAT2 for ubiquitination and degradation, while Morbilliviruses and Henipaviruses V proteins essentially impair STAT1/2 phosphorylation, activation and nuclear translocation. In addition, Morbilliviruses and Henipaviruses also encode for C proteins of which role in the inhibition of IFNa/b response has been a matter of debates [34] [35] [36] [37] . Recent reports showed that Morbillivirus C proteins only have a minor role in the inhibition of IFN-a/b signaling [37] , but are essential to block IFN-a/b induction [38] . Whether Henipavirus C proteins can directly block IFN-a/b or promote viral replication through alternative mechanisms is unclear [35] . In contrast, it has been clearly established that Respirovirus C proteins are potent inhibitors of IFN-a/b signaling [5, 18, [39] [40] [41] . In this report, we show that hPIV3-C, but not MV-C or Nipah-C, directly interacts with STAT1 and efficiently inhibits IFN-a/b signaling. In addition, we identified a minimal STAT1 binding domain that encompasses AA 90-195 of hPIV3-C, a region suspected to fold into a coiled coil. Interestingly, this conserved domain is localized within the STAT1 binding region shared by all four isoforms of Sendai virus C protein [32] . Together, these results confirm the capacity of hPIV3-C to block IFN-a/b signaling pathway [18] , provide molecular basis to this inhibition and clarify the fact that Respirovirus C proteins are functionally distinct from Morbillivirus and Henipavirus C proteins.