The purpose of this study was to ascertain the views of pre-service mathematics (PSM) teachers on the use of portfolios as an alternative assessment method. This study was conducted with 146 Turkish PSM teachers participating in a semester-long portfolio assessment application. Data were collected with a questionnaire comprising 34 items on a 5-point Likert-type scale. Data were analyzed using SPSS 15.0 software and presented with frequency and percentage. The findings indicated that most of the PSM teachers believed that the portfolio assessment application facilitated an active learning process, allowed them to monitor their progress and to remedy their deficiencies, and to gain professional knowledge and experiences in portfolio assessment method. However, it was determined that they were most challenged by time management. This study revealed that use of the portfolio assessment contributed to the PSM teachers' individual, social, and professional development. (Contains 4 tables.)