At present, Taiwan is actively promoting the evaluation of teachers’ expertise in elementary and middle school. One of the difficulties that has been encountered is the lack of valid assessment programs and tools. The goal of this article is to introduce and analyze a method of appraising teachers now used by the National Board of Professional Teaching Standards (NBPTS) in the USA: the use of teaching portfolios as an evaluation tool. We critically analyze the benefits and costs of using teachers’ portfolios for teacher appraisal, and then propose five implications from NBPTS experiences for Taiwan policy makers: 1) setting up the teaching professional standards which are applicable for domain-independent and domain-specific expertise; 2) the teacher appraisal should include instructors’ teaching as well as students’ learning; 3) implementing teaching portfolios as a tool for professional evaluation and professional development; 4) using show-case portfolios and evaluation portfolios sequentially to enhance teachers’ acceptance of the portfolio as a tool of assessment ; 5) utilizing both qualitative and quantitative methods to assess the effectiveness of the program of teaching portfolios evaluation.