The shielded metal arc welding process (SMAW) is simple, versatile, cheap and can be applied to almost all kind of alloys including duplex stainless steels. However, high corrosion resistance and excellent mechanical properties combination of these steels may be severely impaired if suitable welding procedures are not taken into account. The literature indicates as correct, a large range of heat inputs over 0.5–2.5kJ/mm, which is still very vague. This paper was intended to study the influence of two heat inputs (0.6 and 1.0kJ/mm) on the properties of UNS S31803 duplex stainless steel welded joints. Microstructural changes, mechanical performance and corrosion resistance of welds have been characterized. Moreover, the influence of a second pass on root pass properties has been also evaluated. Results showed that the best combination of properties occurred for low heat input condition.