The integration of selective catalytic reduction catalysts (SCR) into diesel particulate filters (DPF) is an emerging technology in the treatment of nitrogen oxides (NOx) and particulate matter (PM) emissions in diesel exhaust after-treatment. This is driven by ever-tightening limits on NOx and PM emission. In an integrated SCR on DPF, the SCR catalyst is either incorporated as a layer on the wall of the DPF, or extruded within the porous walls of the filter. The compact, low weight/volume of the integrated unit provides improvement in the diesel engine’s cold start emission performance. Experimental investigations have shown comparable performance with standard SCR and DPF units in terms of NOx conversion and PM control. The modelling of the integrated unit however is complicated. The main challenge is how to best capture the complexity of the physical phenomena in a simplified but adequate representation. This paper reviews the approaches to SCR-on-DPF modelling obtained from published materials. It reviews the modelling of SCR-on-DPF against a backdrop of current and historical approaches to modelling standard SCR and DPF units. Some of the methods that have been attempted for model solutions are also reviewed. This work presents the state of the art of SCR-on-DPF modelling and can serve as a resource for new researchers in SCR-on-DPF modelling.