This chapter uses a phenomenographic research approach and analyses 84 pre-service secondary teachers’ written responses to the questions: (1) What is a model?; (2) What is a mathematical model?; and (3) What does it mean to engage in mathematical modelling? Through the use of open-, axial- and selective coding, the emerging categories capture the variation of the pre-service teachers’ pre-conceived views of the notions of models and modelling. The results show that mathematical models were elaborated on in terms of descriptions, representations and explicit examples of models, models being tools, didactical aspects of models and encapsulating the structure of mathematics itself. Modelling was found to be expressed as the use of mathematics and/or models, to create general mathematical models, in term of the whole/part of the modelling process as well as didactical aspects and meta-perspective of teaching mathematics.