A facile synthetic approach to segmented polysulfone-containing polyesters affords a versatile family of high-temperature thermoplastics with tunable thermomechanical properties. End-capping of phenol-terminated polysulfone (PSU) using ethylene carbonate generated telechelic oligomers with primary alcoholic functionality. Melt transesterification of dimethyl terephthalate and 1,4-butanediol in the presence of PSU oligomers yielded high molecular weight segmented block copolymers with alternating PSU and poly(butylene terephthalate) (PBT) sequences. Systematic variation in PSU incorporation resulted in tunable PBT segment length and accompanying thermal properties. DSC and SAXS elucidated a miscible, amorphous PSU and PBT phase, and PBT crystallinity remained below an 80 wt % incorporation of PSU. Dynamic mechanical analysis (DMA) revealed a crystallinity-dependent plateau regime above the copolymers glass transition temperature (Tg), while SAXS and WAXD confirmed a semicrystalline morphology below 80 wt % PSU. Incorporation of PSU segments significantly affected the crystallization and thermomechanical properties of PBT, and as a result these copolymers offer impact as chemically resistant, high-temperature thermoplastics due to their crystallinity, thermal stability, and high-temperature operating window.