SignificanceNanobodies are a promising class of biologics that can be used to prevent or treat viral infections. Here, we describe the production and validation of a discovery library that produces single-domain nanobodies using an engineered human antibody variable gene segment. As a test case, anti-SARS-CoV-2 nanobodies were isolated from this library and pairs of complementary nanobodies were incorporated into an antibody-like molecule that targets the receptor-binding domain using a biparatopic mode of engagement. This modular bispecific format enabled the rapid testing of nanobody pairs, and we show that incorporating pairs of nanobodies with different specificities can have synergistic effects on neutralization breadth and potency.