Novel biodegradable amphiphilic ABC 3-miktoarm star terpolymers composed of poly(epsilon-caprolactone) (PCL), monomethoxy poly(ethylene glycol) (MPEG), and polyphosphoester (PPE) were synthesized by a combination of ring-opening polymerization and "click" chemistry. MPEG was first end-capped by epoxide ring, which was opened by sodium azide in the presence of ammonium chloride to give modified MPEG bearing reactive azide and hydroxyl groups (MPEG(-OH,-N-3)). "Click" chemistry was then applied to conjugate alpha-propargyl-omega-acetyl-poly(epsilon-caprolactone) and MPEG(-OH,-N-3), resulting in a diblock copolymer of MPEG and PCL with reactive hydroxyl groups at the junction point (MPEG(-OH)-b-PCL), which further initiated ring-opening polymerization of 2-ethoxy-2-oxo-1,3,2-dioxaphospholane (EEP) under the catalytic action of stannous octoate to obtain the desired well-defined (MPEG) (PCL) (PEEP) 3-miktoarm star terpolymers. Such terpolymers and their intermediates were characterized by H-1 NMR, FT-IR, and gel permeation chromatography. These polymers are expected to be promising vehicles for drug delivery applications.