This work analyzes the effect of temperature on the anaerobic digestion of sugar beet by-products for both biohydrogen and biomethane production. The findings demonstrate that the anaerobic process was significantly affected by the increase in temperature from mesophilic to thermophilic or hyper-thermophilic conditions. Therefore, it was found that the mesophilic temperature was more suitable for the anaerobic digestion of sugar beet by-products, using either the raw feedstock or the pretreated feedstock at higher temperatures. The specific production of biohydrogen from thermophilic acidogenic digester was 1.7 fold higher than that obtained from the hyper-thermophilic one. Moreover, when raw feedstock was used in single stage digesters, a methane production rate of 0.55 LCH4/Lr*d was obtained from the mesophilic digester, which was 45% higher than that of the thermophilic one. It has been observed that the increase in temperature led to a high accumulation of volatile and long chain fatty acids, inhibiting and slowing down the anaerobic process.