In the present paper, the flow of adhesives in composite Pi-joints is investigated numerically and experimentally. A model is developed to simulate the flow process using a computational fluid dynamics code. The results from this model are validated against matching experimental work. The viscosities of a number of adhesives were measured and found to be Non-Newtonian in character. A Non-Newtonian power law approach was found to represent the adhesives' viscosities very well. Based on the rheological data a material model was developed and implemented in the numerical code. The numerical predictions and the experimental results were found to be in good agreement. The model developed can be used to investigate the effect of various process parameters, such as insertion speed, insertion force and adhesive viscosity on output variables, including insertion force and the pressure distribution in the Pi-slot. The numerical model enables relatively simple investigations of process parameters, thus providing an efficient and useful tool to guide the bonding process design and control.