A putative way of the protective action of cytokinins on the photosynthetic processes in crops experiencing various stress factors is considered. Various cytokinins are characterized. Pathways of the multiple effects of cytokinin preparations mediating the protection of the photosynthetic machinery from stress are described. Cytokinins interact with receptor proteins, and then the signal is transduced to primary cellular targets (primary response genes). These genes, which possess receptor domains, induce synthesis of the corresponding mRNAs and photosynthesis-related proteins of chlorophyll-protein complexes, the electron-transport chain, and carbon metabolism, primarily, the key enzyme ribulose bisphosphate carboxylase/oxygenase. The protective action of cytokinins under stress conditions preserves the structure and function of the photosynthetic machinery. The application of cytokinins to improving crop yields is discussed.