Styrene maleic anhydride copolymer (SMA) with higher MA content (21.8 wt %) than reported SMA (mostly 8 wt %) was used as a compatibilizer for poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)/polyamide 6 (PA6) blends by in situ formed PA-g-SMA during melt processing. The tensile strength and flexural strength of PPO/PA blends were greatly increased by the addition of SMA. The morphology of PPO/PA/SMA (30/70/variable) was investigated by scanning electron microscopy, and the addition of SMA led to a significant decrease in the particle size of the dispersed PPO phase. Melting and crystallization of PPO/PA/SMA blends were studied by differential scanning calorimetry, and the results showed that the addition of SMA could improve the compatibility between PPO and PA. The in situ reaction between PA and SMA was confirmed by Fourier transform infrared analysis. SMA was an effective compatibilizer for PPO/PA blends, and its compatibilization mechanism was discussed. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 3545-3551, 2010