In this study, stereocomplex-type poly(l-lactide) (SC-PLA)/organo-modified layered zinc phenylphosphonate (m-PPZn) nanocomposites were synthesized and characterized as a new material for green material usages. A long-chain oleylamine was selected to modify layered zinc phenylphosphonate (PPZn). The structural arrangement of the original and oleylamine-modified PPZn was determined using wide-angle X-ray diffraction (WAXD), and m-PPZn exhibited a large interlayer spacing of 30.3 . The correlation length of PPZn derived using several orders of peak profiles decreased with oleylamine addition, suggesting that the structural arrangement of m-PPZn exhibits less perfect alignment. The mechanical properties, structure, and morphology of the SC-PLA/m-PPZn nanocomposites were characterized with dynamic mechanical analysis, WAXD, and transmission electron microscopy (TEM). Both WAXD and TEM results demonstrate that most of the layered materials of partial delamination are randomly dispersed in the SC-PLA matrix. Mechanical properties of the fabricated 1 wt% SC-PLA/m-PPZn nanocomposites show significant enhancements in the storage modulus when compared to SC-PLA matrix. The biodegradability of SC-PLA/m-PPZn nanocomposites was studied with Trizma buffer solution containing proteinase K. It has been shown that the SC-PLA/m-PPZn nanocomposites exhibit a much higher disintegration rate than that of the SC-PLA matrix.