This research applies the heuristic–systematic model to understand how country-of-origin (CO) cues can affect the way consumers process advertising messages and evaluate advertised products under different conditions. Findings of Experiment 1 show that, when product information is ambiguous, consumers are more likely to engage in heuristic processing, relying on CO cues to infer product quality and form their product evaluations. However, when product information is unambiguous, consumers engage in systematic processing and evaluate the product based on their assessments of product attributes. Findings of Experiment 2 further suggest that product involvement affects the extent to which consumers engage in heuristic processing when message ambiguity is at different levels. Specifically, mediational analyses indicate that, when product information featured in an ad is ambiguous, a low-involving product engages consumers in heuristic processing. Furthermore, when product information is unambiguous, a low-involving product engages consumers in systematic processing, whereas a high-involving product involves participants in an additivity processing style in which CO cue-based heuristic processing and attribute-based systematic processing co-occur.