Cereals are the most important crop plant supplying staple food throughout the world. The economic importance and continued breeding of crop plants such as rice, maize, wheat, or barley require a detailed scientific understanding of adaptive and developmental processes. Protein phosphorylation is one of the most important regulatory posttranslational modifications and its analysis allows deriving functional and regulatory principles in plants. This minireview summarizes the current knowledge of phosphoproteomic studies in cereals.