Problem Statement: Traditional forms of assessment such as essays and end of term examinations are still widely used in higher education in Ireland as the sole assessment method. These forms of assessment, while they may be valid and reliable approaches for collecting evidence of the acquisition of theoretical knowledge, rarely afford students the opportunity to apply knowledge to key professional scenarios. In the context of teacher education, if the aim is to develop teacher competence beyond the mere possession of technical skills then appropriate pedagogic and curriculum interventions need to be developed, implemented and evaluated. Purpose of Study: This paper argues that reflection and experiential learning should be infused through effective assessment strategies and embedded in the training and formation of trainee-teacher attributes. The authors draw on their experience as lecturers and module/course designers for an "Assessment" module within a teacher-training degree programme in a School of Education in the Republic of Ireland. Methods: This paper presents the findings of a 4-year study, which adopted a multi-methods approach. The research was conducted using both numerical and qualitative tools. A primary focus of the research used student reflection to generate relevant data suitable for analysis and this was then triangulated with module evaluations and numerical performance data. The paper describes the research that used constructivist principles to help foster the development of assessment competence through a cycle of action/critical reflection/revised action within an assessment portfolio design. Findings and Results: The research demonstrates that a learner-centred approach to assessment not only helps the student/trainee teacher in the development of their own professional competence but also shows teacher educators that they need to experience learning and reflection at a deep level in order to be able to develop the professional competence required of them as future teachers. Conclusions and Recommendations: Those students who participated in the study expressed their appreciation of the value of portfolio assessment and indicated that they would be prepared to use it in their future professional contexts. The research suggested that a number of recommendations be considered and these include enabling students to make sense of knowledge through reflection, and the design of assessments, which replicate authentic professional scenarios and require decision-making, in order to assist in developing a reflective capacity for appropriate professional judgment.