Objectives: This study investigated individual and situational factors that may make observing positive treatment of an ingroup member attributionally ambiguous and cognitively taxing for ethnic minority perceivers. Method: 163 Latino/a participants who varied in the perception that Whites are externally motivated to behave positively toward minorities (Perceived External Motivation Scale; PEMS) observed a Latino candidate selected over 2 White candidates by a White Human Resources officer. The selected candidate was or was not the most qualified and a diversity rationale was or was not provided. Participants subsequently performed a test of cognitive interference. Results: When a less-qualified minority candidate was selected, the presence (vs. absence) of a diversity rationale increased cognitive interference among low PEMS participants, but decreased cognitive interference among high PEMS participants. Results suggest that a diversity rationale made the selection of a less qualified minority more ambiguous for low PEMS but less ambiguous for high PEMS participants. Conclusions: The present study informs our understanding of when and for whom Whites’ positive behavior is perceived as attributionally ambiguous.