Nanobodies (Nbs) are naturally occurring single-domain antibody fragments from camelid heavy-chain antibodies. They have unique biophysical properties, including small size and thermostability, that allow aerosolized administration. In this preprint, Gai et al. describe Nb phage display libraries from camels immunized with the SARS-CoV-2 spike receptor-binding domain (RBD). Out of 381 Nbs identified, 7 blocked the interaction between the virus entry receptor ACE2 and 8 RBD variants. Nb11-59, a candidate with the highest neutralizing activity, was further selected to validate its interaction with the RBD by structure prediction analysis. Production of Nb11-59 in a yeast expression system followed by its nebulization showed potential for rapid and high-quality manufacturing.