Amino acid-based poly(ester amide) (PEA) macromers (e.g., functional PEA macromers) and methods for preparing amino acid-based poly(ester amide) (PEA) macromers. The functional PEA macromers can comprise functional groups such as hydroxyl, amine, sulfonic acids, carboxyl, thiol and acryloyl at the two terminuses of the PEA macromers. The content of the terminal functional groups on the macromers can be precisely controlled by adjusting the molar ratio of reactive monomers. The resulting versatility of these new functional PEA macromers can be used to fabricate a wide range of PEAs and PEA hybrid derivatives with very different chemical, physical, mechanical, thermal and biological properties. The functional PEA macromers can also be polycondensed into forming block PEA polymers.