The emergence of human coronaviruses (HCoVs), especially the current pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), engender severe threats to public health globally. Despite the outstanding breakthrough of new vaccines and therapeutic medicines in the past years, HCoVs still undergo unpredictable mutations, thus demanding more effective diagnostic and therapeutic strategies. Benefitting from the unique physicochemical properties and multiple nano–bio interactions, nanomaterials hold promising potential to fight against various HCoVs, either by providing sensitive and economic nanosensors for rapid viral detection, or by developing translatable nanovaccines and broad-spectrum nanomedicines for HCoV treatment. Herein, we systemically summarized the recent applications of nanoagents in diagnostics and therapeutics for HCoV-induced diseases, as well as their limitations and perspectives against HCoV variants. We believe this review will promote the design of innovative theranostic nanoagents for the current and future HCoV-caused pandemics.