This paper reports findings from a Fijian study that engaged secondary mathematics teachers in a two-day professional development workshop on the use of portfolios as an alternative means of assessing student learning in mathematics. Utilising an action research approach with a view to involve teachers as key stakeholders in mathematics education, the professional development prompted a small group of secondary mathematics teachers to think about the mathematics content and processes which could not be assessed using written tests, and to develop assessments that would reflect higher-order thinking in mathematics. While the majority of the teachers came up with ideas that were well suited for portfolio assessment, some participants faced minor difficulties in relating to real-world experiences and developing higher-order tasks. Teachers were able to come up with teaching and learning activities that could be used for portfolio assessment. At the end of the workshop ten of the 12 teachers were interviewed to gain an insight into their experiences. All of them stated explicitly that they had found the workshop very useful and rewarding because portfolios could provide an alternative way to assess student learning, and could possibly influence the way they taught mathematics.