Plant proteins are essential for providing high-quality sustainable nutrition. Extraction and processing of plant proteins reduce their functionality. For this, several modification methods are applied to improve the overall quality of the protein isolates and food products based on them. Chemical method of protein modification is one of the oldest concepts and is identified as most effective for the derivatization of the side chain with suitable functional groups to impart and improve important functional properties of plant proteins. Chemical modification methods such as glycation, phosphorylation, acetylation, and succinylation, pH shifting, among others, are found to be effective with various plant proteins such as pea, soyabeans, zein, rice protein, and other bean proteins. Each method influences the secondary and tertiary structures of plant proteins, which can be evaluated by biophysical methods like Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopy. Based on the nature of the functional group incorporated in the plant protein, the chemically modified proteins are improved in their various techno-functional properties, like solubility, surface hydrophobicity, gelling, emulsification, water retention, and thermal stability. The chemical modification method is a cost-effective and efficient process. However, disadvantages such as toxic chemical utilization and by-product generation limit their extensive application. These can be addressed by using edible and safe organic chemical agents. The requirement of regulatory bodies for clean label status is essential for protein modification techniques, and hence needs careful consideration while producing and commercializing food products incorporating chemically modified plant proteins.