In this work, the effect of pretreatment on the biochemical methane potential (BMP) of sweet sorghum biomass was determined. Various pretreatment methods, such as thermal (1 h at 121 °C), enzymatic [through the addition of the enzyme Celluclast 1.5L (Cellulase from Trichoderma reesei, ATCC 26921) or by the addition of a mixture of Celluclast 1.5L and Novozyme 188 (Cellobiase from Aspergillus niger) at a ratio of (3:1)], chemical [through alkali (NaOH) or acid (H2SO4) addition, at concentrations of 0–2 % w/v] or combination of the above methods (thermal acid and thermal alkaline) were tested, in order to evaluate their effect on carbohydrate solubilization (saccharification) and on the methane yield. The experimental results showed that thermal acid treatment and enzymatic treatment for all enzymes concentrations tested improved saccharification. Under thermal alkaline treatment at NaOH concentrations above 0.5 % w/v, a significant decrease in soluble carbohydrates concentration was observed meaning that a high portion of sugars also contained in sorghum biomass was degraded or was transformed into other components. BMP experiments showed that the chemical pretreatment methods did not enhance methane generation compared to the raw substrates. This could be attributed either to inhibitory compounds released during pretreatment, or to high salts (cations of sodium during alkaline treatment) concentration, causing in both cases methanogenic bacteria inhibition. On the other hand, thermal treatment improved the methane yield from 253 to 288 LCH4/kg sorghum. During enzymatic pretreatment, the methane production was enhanced either with only one or with the mixture of enzymes.