Cold stress is a major environmental constraint that limits nut productivity worldwide. Late spring frost is identified as a yield-reducing factor in Persian walnut production as well. Despite significant improvements in cold and freezing tolerance methods, orchardists have not taken advantage of these recommended protection methods. This study examined determinants of walnut orchardists’ frost-protection behavior, using the extended theory of planned behavior (TPB) as a conceptual framework. Based on TPB assumptions, frost-protection behavior is mediated by a series of constructs. The purpose of this research was to examine the role of TPB variables (extended by orchard-system profile) in meeting the necessities of performing active and passive methods of frost protection. A total of 91 orchardists completed a baseline questionnaire that included the TPB constructs. The present investigation was carried out in the major walnut growing site of Sepidan County, western Fars Province, Iran. The results from the hierarchical multiple regression showed that the behavioral attitude, perceived behavioral control (PBC), intention, orchard-system profile, and interaction of orchard-system features and PBC were significant predictors of frost-protection behavior in the prospective sample. Results of the present study provided evidence that the extended TPB is a useful framework for understanding orchardists’ frost-protection behavior.