<p>Empirical evidence gathered across decades has demonstrated that characteristics of the person, characteristics of the situation, and interactions between the two jointly affect human behavior. Person x situation interaction effects are often as strong as or stronger than the main effects of the person or the situation. Despite this compelling evidence, interactionist research on justice behavior is rare. Moreover, virtually all interactionist justice studies have considered only linear interactions between functionally equivalent person and situation factors. However, the linear interaction model cannot account for behaviors with limited ranges of intensity or frequency. To solve this problem, I present the Nonlinear Interaction of Person and Situation (NIPS) model. Additionally, I recommend three strategies for enhancing person x situation interaction models. First, the explanatory potential of interaction models can be increased by linking their parameters with perceptual, attentional, social cognitive, motivational, and emotional mechanisms that generate interactions. I present an advanced version of the NIPS model for this purpose. Second, incorporating personality and situational factors with incremental impact on relevant outcomes increases the complexity of interaction models, allowing for a more comprehensive understanding of justice behavior. Third, I delineate a dual process person x situation interaction model that can account for both automatic and controlled components of justice behavior. Applications of this model require the indirect assessment of implicit dispositions in addition to the standard direct assessment of explicit dispositions.</p>