Materials used in car body production are joined by resistance spot welding as the dominant method of joining. Significant changes occur in mechanical and metallurgical properties of the weld nugget and heat affected zone during welding process. The research into these changes is very important for estimation of optimal welding parameters to ensure the required quality of welded joints. The paper deals with the problems of weldability of high strength dual-phase steel sheets used in the car body production. Dual-phase steel was developed specifically for automotive industry to benefit from its formability and crash absorption ability in comparison with conventional advanced high-strength steels. Weldability of dual-phase steel is one of the key factors governing its application in automotive industry. The influence of the resistance spot welding parameters, mainly welding current and welding time, on the weld quality was investigated by visual control, static tension test, and structural analysis of the joints and microhardness measurements.