It has been observed that the pressures of globalisation and the lure for increased profitability have continued to motivate South African multinational companies (MNCs) to invest across international borders, especially in the Southern African Development Community (SADC). Furthermore, the deliberate policy to integrate the region has necessitated most of the governments of the SADC to encourage their largest companies to invest within the region, in order to tap from improved incentives created by the regional economic integration arrangement. Using both aggregate and firm level dataset from various sources between the period 1980 and 2011 in various econometric estimations, this study uncovers that there is correlation between the value of South African MNCs' contribution to regional economic development and investment in the SADC. The main results from this study shows that South African MNCs contributes positively to regional economic development and investment in the region. Similarly, the findings of this study indicate that South Africa-originated MNCs operation within the region triggers the growth of the cumulative GDP of this region. The causality test affirmed the statistical significance of these relationships, and also ensured that spurious correlations did not impede the econometric estimation procedure.