Morphology and properties of poly(butylene terephthalate) (PBT)/nylon 6 (PA6)/EVA-g-MAH ternary blends were investigated. The blends were prepared in a corotating, intermeshing, twin-screw extruder. The incorporation of maleic anhyride (MAH) grafted onto ethylene-vinyl acetate copolymer (EVA) (EVA-g-MAH) in the PBT/PA6 binary blends decreased the tensile and flexural strength but increased the impact strength, while the mechanical properties of the PBT/PA6 blends were decreased with increasing PA6 content regardless of the presence or absence of the EVA-g-MAH. The morphology studies of the ternary blends showed gross phase separation. The rheological properties of the ternary blends suggested that excessively high reactivity between amine end groups of PA6 and MAH grafted onto EVA makes the compatibility between PBT and PA6 worse, although EVA-g-MAH was expected to work as a compatibilizer for PBT/PA6 blends. The degree of reactivity between functional groups in PBT, PA6, and EVA-g-MAH was also examined by investigating the effect of blending sequence on the properties of the ternary blends.