<p>Individuals frequently adopt self-defensive behaviors to mitigate the threat of air pollution, playing a crucial complementary role to governmental pollution control. Understanding the mechanisms and determinants of these behaviors is therefore key for effective policy-making. While prior research has established a link between risk perception and behavior, it has largely overlooked themagnitude, direction, and impact of perceptual bias. This study addresses this gap by examining the discrepancy between subjective air pollution assessments and objective pollution levels. We focus specifically on how perceptual biases—operationalized as overestimation or underestimation—influence self-defensive behaviors. Our findings reveal that income, education, pollution exposure, and access to information are significant moderators of these biases. By conceptualizing perceptual bias as a critical and moderated construct, this study advances theories of pro-environmental behavior. We propose targeted interventions, such as improving the accessibility and clarity of environmental information, enhancing public knowledge, and designing interventions tailored to regions with varying pollution levels. These findings contribute to a deeper integration of perceptual biases into pro-environmental behavior theories and offer practical recommendations for promoting appropriate self-defensive behaviors.</p>