Complexity thinking is relatively new to education research and has rarely been used to examine complex issues in physics and engineering education. Issues in higher education such as student retention have been approached from a multiplicity of perspectives and are recognized as complex. The complex system of student retention modelling in higher education was examined to provide an illustrative account of the application of complexity thinking in educational research. Exemplar data was collected from undergraduate physics and related engineering students studying at a Swedish university. The analysis shows how complexity thinking may open up new ways of viewing and analysing complex educational issues in higher education in terms of nested, interdependent and interconnected systems. Whilst not intended to present new findings, the article does illustrate a possible representation of the system of items related to student retention and how to identify such influential items.