Abstract In the tandem pulsed gas metal arc welding, the occurrence of arc interruption by the electromagnetic interaction between the two adjacent arcs becomes a problem. In order to clarify this problem, effects of interwire distance and Ar–CO2 gas mixture ratio on an abnormal arc voltage and arc interruption are investigated. The abnormal arc voltage and the arc interruption frequently occur with pulse peak currents which are supplied alternately to two wires. In addition, both phenomena occur in trailing arc which is located on molten pool at base current duration remarkably. There is most number of abnormal arc voltage and arc interruption times in trailing when the interwire distance is 10 mm, because a deflected length of trailing arc by the electromagnetic interaction becomes the longest. Moreover, the CO2 mixture ratio in shielded gas affects the occurrence of abnormal arc voltage and arc interruption. The abnormal arc voltage and arc interruption do not occur when CO2 gas mixture ratio is equal to or less than 5%. However, number of abnormal arc voltage and arc interruption times increase rapidly with increasing CO2 gas mixture ratio when CO2 gas mixture ratio is over 10%.