Evasive knowledge hiding (EKH) is a behavioural phenomenon with important personal and organizational implications, whose intraindividual motivational antecedents and situational contingencies are still not sufficiently clarified. In this paper, we integrate mixed-motives and trait-activation theory to address EKH in low- and high-trust work relationships. The focus is on complex interactions of trait competitiveness and prosocial motivation while responding to a knowledge-seeking request by a (dis)trusted colleague. Our findings based on three mixed-methods studies (two factorial survey field studies and one quasi-experimental student-based study) provide general evidence of the overwhelmingly positive effect of trait competitiveness (i.e., pro-self motives) on EKH across situations. Additionally, we found that if competitive individuals are also prosocially motivated, their “paradoxical personality” will manifest in less EKH behaviour, especially if situational trust cue is positive. Implications for research and practice are discussed.