The glass transition behaviour, microphase separation morphology and crystallization of poly(vinyl alcohol)-g-poly(methyl methacrylate) graft copolymers (PVA-g-PMMA) were studied. A lamellar microphase separation morphology was formed, even for a copolymer containing only 28 wt% PVA. An unusual glass transition behaviour of the copolymer was found : the glass transition temperature (T(g) of PMMA microphase did not move towards the lower T(g) of PVA, but increased markedly to as much as 20 K higher than the T(g) of the PMMA homopolymer. The crystallization of the PVA microphase of the copolymer was also investigated.