The aim of this study is to identify the modelling teaching competencies that the beginning in-service secondary mathematics teacher developed in the process of improving the lesson dealing with ‘word problems’ towards modelling lesson. Modelling lesson improvement was carried out in 5 steps based on the expansive learning process proposed by Engeström. Then, we analysed what modelling teaching competencies were developed through these steps, based on 4 dimensions and sub-items by Borromeo Ferri. This paper reported the results for teacher A. The results showed that in the process of improvement towards modelling lesson, the development of modelling teaching competencies was identified in all 4 dimensions, although not in all sub-items. It is expected that teacher training for beginning in-service secondary mathematics teachers with no modelling experience will be developed.