This article tests whether individual differences in inferring one trait from another (intertrait inferences) can be linked to lay beliefs about the malleability of personality (person theories). It finds that holding the belief that personality is malleable (incremental theory) rather than fixed (entity theory) at the time of inferences is associated with less extreme inferences involving semantically related (but not unrelated) traits. Although person theories have been assumed to be stable over time, existing short-term test-retest coefficients do not capture their instability over a longer period. These results can illuminate interrater discrepancies in assessments of personality pathology and job performance, enrich understanding of such phenomena as stereotyping and impression formation, refine the interpretation of past research involving person theories, and inform research planning.