Short-chain-length medium-chain-length polyhydroxyalkanoate (SCL-MCL PHA) copolymers are promising as bio-plastics with properties ranging from thermoplastics to elastomers. In this study, the hybrid pathway for the biosynthesis of SCL-MCL PHA copolymers was established in recombinant Escherichia coli by co-expression of β-ketothiolase (PhaARe) and NADPH-dependent acetoacetyl-CoA reductase (PhaBRe) from Ralstonia eutropha together with PHA synthases from R. eutropha (PhaCRe), Aeromonas hydrophila (PhaCAh), and Pseudomonas putida (PhaC2Pp) and with (R)-specific enoyl-CoA hydratases from P. putida (PhaJ1Pp and PhaJ4Pp), and A. hydrophila (PhaJAh). When glycerol supplemented with dodecanoate was used as primary carbon source, E. coli harboring various combinations of PhaABCJ produced SCL-MCL PHA copolymers of various monomer compositions varying from C4 to C10. In addition, polymer property analysis suggested that the copolymers produced from this recombinant source have thermal properties (lower glass transition and melting temperatures) superior to polyhydroxybutyrate homopolymer.