The transitional process of flow and heat-transfer in a circular pipe fitted with a short static mixer was studied with Newtonian and pseudo-plastic fluids. An experimental formula, which was derived from the same concept as a well-known transition model of boundary layer flow on a flat plate, coincided well with experimental results of friction and heat-transfer. The transitional Reynolds number in heat-transfer was larger than that in flow for both fluids. In heat-transfer experiments, the transitional Reynolds number for a pseudoplastic fluid was smaller than that for a Newtonian fluid, and heat-transfer augmentation in the transitional region was larger in a pseudo-plastic fluid than in a Newtonian fluid.