In micro-sociology, interactionism is a theoretical perspective that sees social behavior as an interactive product of the individual and the situation. In other words, it derives social processes (such as conflict, cooperation, identity formation) from social interaction, whereby subjectively held meanings are integral to explaining or understanding social behavior.

This perspective studies the ways in which individuals shape, and are shaped by, society through their interactions. Interactionism thus argues that the individual is an active and conscious piece of the social-context system, rather than merely a passive object in their environment. It believes interactions to be guided by meanings that are attached to the self, to others with whom each individual interacts, and to situations of interaction; all of which are altered in interaction themselves. In this sense, interactionism may stand in contrast to studies of socialization, insofar as interactionism conceives individuals to influence groups at least as much as groups influence individuals.

George Herbert Mead, as an advocate of pragmatism and the subjectivity of social reality, is considered a leader in the development of interactionism. Herbert Blumer expanded on Mead's work and coined the term symbolic interactionism.

Through this perspective (under modern techniques), one may observe human behavior by three parts: trait, situation, and interaction (between trait and situation). 'Trait' refers to the extent to which personality directly affects behaviour, independent of the situation (and therefore consistently across different situations); 'situation' takes into account the extent to which all different people will provide basically the same response to a given situation; and 'interaction' involves the ways in which the same situation affects individual people differently.