In this study, poly(lactic acid) (PLA)-based biopolymer foams were prepared through injection molding using the high-pressure foam injection molding method, also referred to as “breathing mold” technique, with the addition of various amounts (0, 1, 2, and 4 wt.%) of azodicarbonamide-based chemical blowing agent (CBA). The prepared samples were analyzed for their macrostructure using computed tomography (CT) while the mechanical properties were determined by flexural and Charpy impact tests. CT analysis revealed a finer foam cell structure and decreasing shell thickness with increasing CBA content. Regarding the mechanical properties, the specific flexural strength and flexural modulus of PLA were improved as a result of foaming; however, this improvement came at the cost of a slight deterioration in impact strength.