Scaling-up of microbial fuel cells (MFCs) operated in a continuous mode requires technology transfer from the lab into the field. The effect of scale-up on the MFC performance was evaluated by comparing the maximum power density and removal efficiency of ethanolamine using two MFC reactors with different working volumes. Experiments using a scaled-up MFC with different organic loading rates (OLRs) in continuous mode were conducted to obtain sustainable electricity production and enhanced treatment capacity with a fixed hydraulic retention time (HRT) of 6.2 h. In comparative experiments to investigate scale-up effects, the maximum power density significantly decreased from 0.24 to 0.085 W m-2 due to the increased surface area on the electrode from 25 to 180 cm2. However, satisfactory removal efficiencies of chemical oxygen demand (COD) and ammonia were obtained in the scale-up MFC experiments in the fed-batch mode with different concentrations of ethanolamine (i.e., 100 and 250 mg L-1). In addition, removal efficiencies of COD and ammonia were significantly influenced by experimental conditions in the continuous mode with different OLRs (0.27, 0.66, and 1.33 g COD L-1 day-1). These results demonstrate the importance of ensuring optimal OLRs as a critical factor for scaling-up an MFC in continuous mode.