Myristoylation is a lipid modification conserved among eukaryotes and involves the addition of a 14-carbon myristoyl moiety to a glycine at the N-terminus of cargo proteins. Since not every protein with an N-terminal glycine is myristoylated, experimental verification is necessary to determine which proteins are indeed myristoylated. Here we describe an in vitro myristoylation assay for the Arabidopsis heterotrimeric G protein alpha subunit, GPA1, as well as the Arabidopsis SALT OVERLY SENSITIVE3. This method can be easily adopted to other proteins of interest.