A series of biodegradable poly(ester amide)s having ether linkages in the main chain were synthesized by ring-opening copolymerization of 3-morpholinone (M) and e-caprolactone (CL) in bulk with stannous octoate, aluminium, isopropoxide, or aluminium isobutoxide as an initiator. The influence of reaction conditions such as polymerization temperature, polymerization time, initiator, and initiator concentration on the monomer conversion and molecular weight are investigated. The comonomer reactivity ratios were determined (M 0.74 and CL 1.28). The water absorption of the polymers increased with increasing M content. In vitro degradation data and the release profiles of 5-Fluorouracil showed that both the degradation rate and drug-release rate increase with an enhanced M content in the copolymers.