Antibodies that antagonize cell signaling pathways specific to their targeted receptor are invaluable tools to study and treat malignancies, but their utility is limited by high production costs and treatment dosages. Researchers have shown that antibodies conjugated to nanoparticles display increased affinity for their target relative to freely delivered antibodies due to multivalency, and this study investigates how this multivalency can enable antibody-nanoparticle conjugates to inhibit oncogenic cell signaling more effectively than freely delivered antibodies. This effect was evaluated using triple negative breast cancer (TNBC) cells that are characterized by hyperactive Wnt signaling mediated through overexpressed Frizzled7 (FZD7) transmembrane receptors. Through analysis of the expression of β-catenin and Axin2, two downstream targets in the Wnt pathway, the results demonstrate that FZD7 antibody-nanoshell conjugates (FZD7-NS) are drastically more effective at inhibiting Wnt signaling in TNBC cells than freely delivered FZD7 antibodies. Additionally, cells treated with FZD7-NS, but not cells treated with freely delivered FZD7 antibodies, have decreased viability, indicating the therapeutic potential of this technology. The results demonstrate that antibody-functionalized nanoparticles can exploit multivalency for improved signal cascade interference over free antibodies, and this may ultimately permit lower antibody dosages to be administered to study signaling pathways or to manage diseases.