The event-related potential (ERP) is a neural response to an internal or external event, and can be obtained by averaging time-locked scalp potentials. The ERP measured in a single trial often has a low signal-to-noise ratio (SNR) because of the relatively large background due to the rhythmic electroencephalogram (EEG) noise. This paper proposes a novel method to enhance ERPs by combining principal component analysis (PCA) with multivariate empirical mode decomposition (M-EMD). EMD is a data-driven time-frequency analysis of nonlinear and nonstationary signals, and M-EMD is its multivariate extension. In the proposed method, PCA reduces the data dimensions, while M-EMD removes the relatively large background EEGs. The performance of the method is evaluated with simulated and measured P300 ERP components obtained from a visual oddball experiment. The results demonstrate that the proposed method can substantially reduce the background EEGs and improve the SNR of P300s. (c) 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.