Polylactic acid (PLA), one of the most promising bio-based materials currently available on the market, has gained much attention recently as an alternative to non-biodegradable synthetic polymers due to its comparable properties and biodegradability. The objectives of this work were to prepare a green composite between PLA and coconut fiber (CF) to investigate an aerobic biodegradation of the biocomposites under controlled composting condition according to the ISO 14855-2. The composites were prepared at various ratios by a twin screw extruder and compression molding, respectively. Based on this research, the maximum content of coconut fiber added was 4 wt%. The addition of coconut fiber can improve the impact strength of the PLA composites. The increasing amount of coconut fiber had no effect on the specific tensile properties. The prototype of biodegradation testing unit - Gravimetric measurement respirometric (GMR) system - was successfully set up according to the ISO 14855-2 standard. The coconut fiber/PLA composite can be degraded significantly, i.e., 60 wt% within only 26 days.