The cellular tail-interacting 47-kDa protein (TIP47) acts positively on HIV-1 and vaccinia virus production. We show here that TIP47, in contrast, acts as a restriction factor for Sendai virus production. This conclusion is supported by the occurrence of increased or decreased virus production upon its suppression or overexpression, respectively. Pulse-chase metabolic labeling of viral proteins under conditions of TIP47 suppression reveals an increased rate of viral protein synthesis followed by increased incorporation of viral proteins into virus particles. TIP47 is here described for the first time as a viral restriction factor that acts by limiting viral protein synthesis.