The use of welded medium-carbon steels is increasing within the oil and gas industry, which requires these materials to resist corrosive environments, extreme temperatures and cyclic loading. This investigation analyzes the effects of Post Weld Heat Treatment (PWHT) upon the mechanical performance of manually arc-welded AISI 1035 (UNS G10350) steel. Rectangular test pieces were machined from carbon-steel piping that had been manually arc-welded using electrode type E6013. These samples were preheated to a temperature of 100 °C, then subsequently heat treated at 300 °C, 450 °C and 650 °C for 1 hour prior to cooling in still air. Mechanical performance of each specimen was assessed via tensile testing utilizing a Testometric machine and hardness assessment using Rockwell testing in accordance with ASTM E18. The results indicated an increase in tensile strength with increasing temperature during heat treatment and maximum tensile strength at 650°C; this was due to the formation of precipitated carbides and stabilization of the weld structure through heat treatment. The stress-strain plots illustrated an increase in flow stress that corresponded to a reduction in the elongation to failure for PWHT specimens; a trend indicative of a strength-ductility trade off. Decreases in Rockwell hardness relative to the as-welded condition were exhibited across all heat-treated conditions; this reflected both relief of residual stresses present within the heat affected zone and tempering of martensitic microstructures within this zone. Overall, the results indicate that heat-treatment parameters may be selected to decrease hardness (and therefore associated SSC/HIC risks), while simultaneously increasing strength for load bearing applications within oil and gas fabrication and/or repair operations involving AISI 1035 components. The relationship between PWHT parameters and material properties will aid in establishing practical guidelines for specification of PWHT within oil and gas fabrication and/or repair operations involving AISI 1035 components.