Abstract: Nitric oxide (NO) is an important signaling molecule regulating diverse biological processes in all living organisms. A major physiological function of NO is executed via protein S‐nitrosylation, a redox‐based posttranslational modification by covalently adding a NO molecule to a reactive cysteine thiol of a target protein. S‐nitrosylation is an evolutionarily conserved mechanism modulating multiple aspects of cellular signaling. During the past decade, significant progress has been made in functional characterization of S‐nitrosylated proteins in plants. Emerging evidence indicates that protein S‐nitrosylation is ubiquitously involved in the regulation of plant development and stress responses. Here we review current understanding on the regulatory mechanisms of protein S‐nitrosylation in various biological processes in plants and highlight key challenges in this field.