During the past decade, increased emphasis has been placed on finding alternatives to IFN-alpha-based therapies. One such alternative, IFN-lambda, has shown therapeutic promise in a variety of diseases, but research of this family of cytokines has been primarily focused on their antiviral activities. The goal of the present study was to investigate the role of IFN-lambda in the regulation and modulation of B cell function. We show that, similar to IFN-alpha, IFN-lambda 1 is able to augment TLR-mediated B cell activation, partially attributed to an upregulation of TLR7 expression, and that both naive and memory B cells express the limiting type III IFN receptor component, IFN-lambda R1. Furthermore, this IFN-lambda-enhanced B cell activation resulted in increased cytokine and Ig production during TLR7 challenge, most prominently after the addition of helper T cell signals. Ultimately, these elevated cytokine and Ig levels could be partially attributed to the increase in proliferation of TLR7-challenged B cells by both type I and type III IFNs. These findings demonstrate the ability of IFN-lambda to boost humoral immunity, an important attribute to consider for further studies on immunity to pathogens, vaccine development, and ongoing advancement of therapeutic strategies aimed at replacing IFN-alpha-based treatments with IFN-lambda.