Background: Members belonging to the interferon-lambda (IFN-${lambda}$) family exert protective action against viral infection; however, the mechanisms of their action have remained elusive. To study IFN-${lambda}$ biology, such as endocytosis of IFN-${lambda}$, we produced monoclonal antibodies (Abs) against human IFN-${lambda}$ and examined their usefulness. Methods: We purified recombinant human IFN-${lambda}$1 expressed in Escherichia coli by using affinity columns. Then, we generated hybridoma cells by fusing myeloma cells with splenocytes from IFN-${lambda}$1-immunized mice. For evaluating the neutralizing activity of the monoclonal Abs against IFN-${lambda}$1, we performed RT-PCR for the MxA transcript. In order to study the binding activity of IFN-${lambda}$ and the monoclonal Ab complex on HepG2 cells, we labeled the monoclonal Ab with rhodamine and determined the fluorescence intensity. Results: Four hybridoma clones secreting Abs specific to IFN-${lambda}$1 were generated and designated as HL1, HL2, HL3, and HL4. All the Abs reacted with IFN-${lambda}$1 in the denatured form as well as in the native form. Abs produced by HL1, HL3, and HL4 did not neutralize the induction of the MxA gene by IFN-${lambda}$1. We also demonstrated the binding of the HL1 monoclonal anbitody and IFN-${lambda}$ complex on HepG2 cells. Conclusion: Monoclonal Abs against IFN-${lambda}$1 were produced. These Abs can be used to study the cellular binding and internalization of IFN-${lambda}$.