Abstract The welding arc behavior in a wire arc additive manufacturing process was studied while building a ten-layer wall over a base plate using a cold metal transfer (CMT) power source. The real-time recorded welding current, voltage, thermal cycles at the base plate, and the synchronized high-speed arc images with each deposited layer were used to understand the arc behavior. A gradual increase in the peak temperature was noticed from the first layer to the fifth layer, and the same decreased with the subsequent deposition of the layers. The intensity of the welding arc was high during the boost phase of the CMT cycle, where most of the base plate and the electrode melting happens. For a given process parameter, the welding arc intensity gradually increased from the first layer to the fifth layer while remained approximately similar from the fifth layer to the tenth layer. The effect of this arc intensity variation was reflected in the consistency of the deposited bead profile. It was observed that the bead width gradually increased from the first layer to the fourth layer and remained approximately the same from fifth to the tenth layer.