A series of experiments was conducted to examine the cathode airflow effect on a direct methanol fuel cell (DMFC) via the views of both airflow rate and airflow velocity from a single cell into a three-cell printed circuit board-based DMFC module. The objective of this paper is to discuss the relationship or difference between a single cell and a planar module. All experiments conducted were under constant anode fuel flow rate and operating temperature. The results show that the airflow supplied to a planar DMFC module does not just multiply the number of membrane electrode assemblies (MEAs) to a suitable airflow rate obtained from a single cell DMFC test. The results also show that the cathode airflow velocity effect is more significant than the airflow rate effect.