Environmental stresses negatively affect crop development, and these scenarios induce an oxidative burst in the plant that can lead to cell death. Nanostimulation is a window of opportunity to promote plant tolerance. Nanostimulants (NSs), such as nanochitosan, nanoparticles, algae and plant nanoextracts and nano-biostimulants can be applied to the seed and/or plant (via foliar or edaphic routes) and enter the plant differentially and interact with cellular structures, or they can be mobilized by vascular bundles. These NSs activate signaling processes such as the promotion of reactive oxygen species (ROS), antioxidant defense systems (enzymatic and non-enzymatic), synthesis of secondary metabolites, and transcript modifications. The present chapter highlights the main results of the use of NSs in the promotion of abiotic stress tolerance and discusses the mechanisms that are promoted in plants under different stressful environments. NSs are an emerging strategy to promote abiotic stress tolerance in diverse crops; their response depends on the type, size, and dose of the nanomaterial, as well as stress conditions. Future studies should be conducted to deepen and standardize the mechanisms of action of NSs and to verify their impact on plant conditions under different stresses simultaneously.