The peltate glandular trichome of sweet basil (Ocimum basilicum L.) is an excellent model system to investigate plant biochemical processes and their regulation. Despite having very similar genomes, the glandular trichomes from different basil cultivars produce very different phenylpropanoid and terpenoid profiles. In earlier studies, several genes involved in the production of these compounds were identified by comparison of their mRNA expression levels across basil lines. In this investigation, proteins and their post-translational modifications in peltate glandular trichomes of basil were identified using a proteomics approach. Cytosolic and microsomal protein samples were prepared from glandular trichomes isolated from four different basil lines, and then analyzed using MudPIT (multidimensional protein identification technology) and GeLC–MS (gel enhanced LC-MS) techniques. Proteins were identified using Sequest and TPP (Trans-Proteomic Pipeline). Post-translational modifications were detected using X!tandem. Protein levels of most of the most highly expressed genes were found to be consistent with the mRNA levels seen in our previous work. Some important enzymes involved in production of phenylpropanoid pathway-derived compounds, such as phenylalanine ammonia-lyase, 4-coumarate:CoA ligase, chalcone synthase 3, and SAM synthetase 1 and 3, were found to be phosphorylated. These results suggest that protein post-translational modification may play an important role in the regulation of production of phenylpropanoids in the glandular trichomes of basil.