Background: The cold/heat questionnaire is one of the most actively developed patient diag-nostic tools in traditional Korean medicine (hereafter abbreviated as TKM) because of itsobjectivity. Unfortunately, the existing questionnaires contain too many items to hold therespondent’s attention. In the current study, we aimed to develop an optimized cold/heatquestionnaire to be used as a complement to the existing questionnaires.Methods: We developed a new cold/heat questionnaire based on a domain analysis of theexisting questionnaires. The questionnaire’s reliability was examined via two test–retestreliability analyses involving 1890 individuals in November 2013 and February 2014. Itsvalidity was examined using a professional cold/heat diagnosis kappa value.Results: The new cold/heat questionnaire consisted of a total of seven items, which werecreated based on an analysis of the existing questionnaires. A reliability analysis performedusing the study participants revealed a correlation coefficient of 0.609, 74.5% agreementwith professional cold/heat diagnoses by TKM practitioners, and a kappa value of 0.487.Conclusion: In the current study, we developed an optimized cold/heat questionnaire. Thelevel of agreement between the questionnaire and professional cold/heat diagnoses by TKMpractitioners was significant, which indicates great potential for its widespread use as adiagnostic tool in TKM.