Protein PEGylation refers to the covalent binding of polyethylene glycol (PEG) moieties to a protein and has been increasingly applied, mainly in the biopharmaceutical industry. This technique may increase bioavailability and stability by decreasing immunogenicity and proteolytic attack. Given the industrial interest and the relevance of this technique, an example of a common PEGylation reaction is herein proposed, using lysozyme as a model protein. This class is divided into three parts: the first one is composed by the PEGylation reaction "per se," the second one aims at the analytical quantification of the PEGylation yield, and the third aims to understand the effects of PEGylation on protein activity. Students should gain skills in comprehending this type of chemical reaction, calculating reaction yields, and realizing the benefits of protein PEGylation. This experimental class comprises two lab classes with the expected duration of 2 h each and is intended for students in the third and fourth years of courses such as pharmaceutical sciences, biochemistry, chemistry, biotechnology, and correlated areas.