The objective of this study was to extract chitin from black soldier fly (BSF) and to convert the substance into chitosan. These products were then used as feed additives and evaluated in an in vitro rumen fermentation system. Extraction of chitin was performed by oil removal procedure, followed by solubilization in acid and alkali solutions under elevated temperature. Conversion of chitin to chitosan was done through a deacetylation step by using NaOH. These products were evaluated in the in vitro rumen fermentation procedure according to the following treatments: control diet, consisted of a mixture between Setaria splendida grass and concentrate 60:40 w/w (CON), CON + chitin 1% (CHI1), CON + chitin 2% (CHI2), CON + chitosan 1% (CTS1) and CON + chitosan 2% (CTS2). Results showed that deacetylation degree of the extracted BSF chitin and chitosan were 33.4 and 61.6%, respectively. Chitosan addition at 1 or 2% decreased total VFA concentration as compared to control diet (P<0.05), but it was not the case for that of chitin. Chitosan addition at 2% reduced IVOMD of the diet by 9.5% (P<0.05). Chitosan addition at 2% level reduced methane emission by 9.0% as compared to control (P<0.05), but the effect was not significant when the compound added at 1%. It is concluded that chitosan derived from BSF reduces methane emission and ruminal feed degradation.