Abstract The sol-gel transition behavior and the degradation behavior of the nanocomposites consisting of laponite clay nanoparticles and poly( d,l -lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly( d,l -lactide-co-glycolide) (PLGA-PEG-PLGA) triblock copolymers (laponite/PLGA-PEG-PLGA nanocomposites) were studied changing the LA/GA ratios of the PLGA blocks in the PLGA-PEG-PLGA. The thermo-responsive sol-gel transition at the physiological temperature (25–37 °C) was observed using the PLGA-PEG-PLGA with a high PEG/PLGA ratio of ∼0.8 regardless of the LA/GA ratios (LA/GA: 1.1, 4.0, and 8.8). The decomposition rates of the laponite/PLGA-PEG-PLGA nanocomposites at 37 °C were regulated by adjusting the LA/GA ratios (LA/GA: 1.1, 4.0, and 8.8). Specifically, ∼45% of the weight loss was observed after 10 days of the decomposition for the laponite/PLGA-PEG-PLGA nanocomposites with the LA/GA ratio of 1.1, while ∼30% of the weight loss was observed after 10 days of the decomposition for the laponite/PLGA-PEG-PLGA nanocomposites with the LA/GA ratios of 4.0 and 8.8.