The structural, morphological, cytocompatibility, and biological properties of composites of poly(butylene succinate-co-adipate) (PBSA) and waste black tea fiber (WBTF) were evaluated. To improve the interface adhesion of PBSA/WBTF composites, glycidyl methacrylate (GMA) was used as a compatibilizer for the blending of PBSA and WBTF. The tensile property of PBSA-g-GMA/WBTF composites was higher than that of PBSA/WBTF composites. To assess cytocompatibility, normal human foreskin fibroblasts (FBs) were seeded onto each type of composites. Results of the FB proliferation assays indicated higher cytocompatibility of PBSA/WBTF composites than of PBSA-g-GMA/WBTF composites. Apoptosis was not observed during the assays of FB proliferation on the PBSA-series composites, demonstrating the potential of PBSA/WBTF and PBSA-g-GMA/WBTF composites for biomedical applications. Moreover, WBTF enhanced the anti-oxidant, anti-inflammatory, and anti-microbial activities of the composites. Both the PBSA/WBTF and the PBSA-g-GMA/WBTF composites showed a better biological activity than the PBSA.