The aim of this study is the investigation of the effects of an intumescent system, consisting of ammonium polyphosphate (APP), as a flame retardant additive, pentaerythritol (PER), as a carbonic agent, and nanoclay, as a synergistic agent, on the flame retardancy of plasticized poly(lactic acid) (PLA). In accordance with this purpose, plasticized and flame retarded PLA with APP compound was prepared and used as a control sample. Nanoclay loading levels were changed between 3 and 10 wt.% in the PLA/APP/PER samples. Samples were produced using extrusion and injection molding techniques. The morphological, thermal, mechanical and flammability properties were studied. The flammability evaluation was performed using limiting oxygen index and vertical burning (UL-94) tests. The obtained limiting oxygen index value was up to 32.9 and UL-94 grade could pass V-0 for samples, containing 3 wt.% of nanoclay. However, increasing nanoclay amount has enhanced the burning time of the sample. The thermal behaviors of the samples were characterized by differential scanning calorimetry. It was shown, that PER incorporation did not significantly change the percentage crystallinity value. The increasing nanoclay loading levels reduced the degree of crystallization. Elongation at break value of sample, containing 5 wt.% of nanoclay, increased by 28%, compared to the control sample.