This article presents the trait of sensory processing sensitivity (SPS), its characteristics, assessment tool and association with psychiatric disorders based on an analysis of the literature on SPS since 1997. An overview of research on SPS in several relevant contexts is presented: evolutionary/adaptive, socio-cultural, temperamental/personality, and biological, taking into account the influence of genetic factors and the activity of specific areas of the central nervous system involved in processing emotional and cognitive stimuli. High sensitivity of sensory processing is an innate trait, biologically determined and modulating developmental processes, occurring in 20–35% of the general population regardless of gender. It is characterized by deeper processing of stimuli, ease of overstimulation, strong emotional reactions and empathic bonds, as well as sensitivity to subtleties in the surrounding world. SPS can be associated with susceptibility to the development of a wide range of psychiatric symptoms and disorders, including depressive and anxiety disorders, social phobia, alexithymia, burnout, internalizing and externalizing disorders and selective mutism in children.