Amorphous PLA nanocomposites based on organic modified kaolinite (KAO) and montmorillonite (MONT) at 4 wt.% were prepared by melt blending and then biodegraded in compost. All materials showed effective degradation in this medium, according to visual observations, DSC and FTIR analysis. The addition of nanoclays was found to increase the PLA degradation rate, especially for kaolinite, due to the presence of hydroxyl groups belonging to the silicate layers of these clays. Addition of MONT to PLA also has a catalytic effect on polymer degradation in compost, but only in the last stages of degradation. In the early stages, MONT tends to delay the degradation of PLA probably due to its higher dispersion level into the polymer matrix as compared to KAO, creating a barrier effect of MONT layers towards water hydrolysis on PLA ester groups.