Let G and H be finite graphs without loops and multiple edges. We use the notation K j×s → (G,H) to mean that if the edges of the complete graph K j×s are coloured by the two colours red and blue, then either the red subgraph of K j×s contains a copy of G, or the blue subgraph of K j×s contains a blue copy of H. The size Ramsey multipartite number m j (P 3 ,K 2,n ) is defined as the smallest natural number s such that K j×s → (P 3 ,K 2,n ). In this paper, we obtain the exact values of the size Ramsey numbers m y (P 3 ,K 2,n ) and m y (P 4 ,K 2,n ) for j ≥ 3.