A study was conducted to investigate the effects of the sintering atmosphere on the superconducting properties of SiC doped MgB2 superconductors. Four different purity Ar gases were chosen as the sintering atmosphere for making bulk samples. It was found that the impurities in the Ar gas resulted in different leves of MgO in the resultant MgB2 superconductors. Superconducting properties, such as the critical temperature (Tc), critical current density (Jc) and upper critical field (Hc2) were affected by the impurity phase inside the samples. Sample phase composition and morphology were analysed to explain the effect of the sintering atmosphere on the sample properties.