Ubiquitination is a vital posttranslational modification that impacts a variety of cellular processes, including the regulation of host–virus interactions and antiviral innate immunity. The ubiquitination of viral proteins plays a role in modulating virus virulence and invasion, while the ubiquitination of host proteins is involved in virus recognition and host–virus interactions, thus influencing antiviral immune responses. Given these diverse functions, there is a growing need to explore the mechanisms underlying protein ubiquitination in the context of host–virus interactions and antiviral innate immunity. Immunoprecipitation after protein denaturation and subsequent immunoblotting with a specific ubiquitination antibody provides a simple and effective method for identifying ubiquitinated proteins during viral infections while minimizing potential interference from interacting proteins. Here, we outline an approach for evaluating protein ubiquitination in HEK 293 T cells during viral infection.