We report an atom-efficient approach to the preparation of sustainable polyesters and their corresponding thermosetting resins (RESINs) from renewable plant oils. Specifically, a diol monomer, oleic acid diethanol amide (OADEA), was derived from high oleic soybean oil (HOSBO) via a powerful amidation reaction. A series of OADEA-derived polyesters were prepared by condensation polymerization of this diol monomer with four different diacids. These polyesters were then epoxidized and cured using anhydrides with the aid of organocatalytic amines, yielding HOSBO-derived RESINs. Both thermal and mechanical properties of RESINs were dictated by the main-chain structures. The curing formulations and conditions were tested extensively to obtain the optimal mechanical properties of thermosetting resins, ranging from plastic to elastomeric properties. Both polyesters and RESINs were fully degradable under basic conditions.