In adopting educational policies that promote portfolio assessment, educational theorists and practitioners have argued that portfolios provide a framework within classrooms where self-regulated learning processes and higher order thinking skills can be nurtured. However, academic research in the field of portfolio assessment has focused largely on issues of design, academic achievement and validity and not on the metacognitive processes that foster self-regulated learning. This thesis presents a case study that explored adult learners' experiences with self-reflection in portfolio assessment. The study explored the substance of adult learners' self-reflections, the reflective strategies they employed and the challenges they faced in constructing their assessment portfolios.