The development of highly efficient modified electrodes is critical for enhancing the power output of microbial fuel cells (MFCs). In this study, different titanium electrodes were modified with functionalized graphene, polyaniline, and their composite (G/PANI) for use in two-chambered MFCs. The results showed that graphene, polyaniline, and G/PANI modification of the cathode improved the maximum power density of MFCs by 74%, 40%, and 126%, respectively, compared with the unmodified control. Among the three materials, G/PANI modification of the anode resulted in the highest open-circuit voltage of MFCs (0.71 V) and recorded the longest operating time for three consecutive cycles (110 h). G/PANI was superior to the other two materials in terms of power generation and it also extended the duration of the operating cycle of MFCs. G/PANI modification of both the cathode and anode improved the maximum power density of MFCs to 124.84 mW•m^-2; this value was 24.8% and 18.9% higher than those obtained by simple modification of the cathode and the anode, respectively. The duration of the operating cycle of MFCs was also markedly extended to 35 h after G/PANI modification of both the cathode and anode. SEM results revealed that the increase in power generation of MFCs with G/PANI-modified electrodes could be attributed to the high surface area of electrodes and the large number of bacteria attached to electrodes. These results have demonstrated that the G/PANI composite can be effective materials for modifying electrodes and improving power generation in two-chambered MFCs.