The purpose of this study was to survey how harmonization is taught in Korean piano lessons and to provide its pedagogical guidelines in teaching harmonization. The questionnaire was made up of two parts. The first part consists of 5 items in multiple choice and yes/no form asking teaching types, experience, the necessity of teaching harmonization, and whether he/she teaches harmonization or not. The second part consists of 5 items in a 4-point Likert scale asking the purpose teaching harmonization, preferring repertoire, expected learning outcomes, and difficulties, etc. And the data was analyzed by frequency of respondents, means and standard deviations for numerical responses, and chi-square analysis for descriptive responses. 501 piano teachers in Seoul, Korea and its suburb areas voluntarily participated and completed the questionnaire. Among 449 piano teachers (89.6%) who felt the necessity of teaching harmonization, 75.90% (N=340) of them actually taught harmonization. The results also found a relationship between teaching experience and evidence of teaching of harmonization where more experienced piano teachers taught harmonization in their lessons. However, in teaching harmonization, few teachers specify what their teaching goals and learning outcomes are. In general, most taught harmonization in order to make music fun. Surveying the musical outcomes after learning harmonization, most Korean piano teachers don't seem to have specific teaching goals of harmonization. For the difficulties in teaching harmonization, most respondents indicated the lack of students' understanding of music theory, lesson time, appropriate teaching materials, and teaching strategies. The result of this study strongly implies that piano teachers are strongly suggested to have concrete teaching goals and teaching strategies of harmonization so that they create more efficient and enjoyable lessons. In addition, it is necessary to develop better and various harmonization materials considering the teaching conditions and the students' characteristics.