The objectives of this study are to: estimate African countries’ Government Openness Index (AGOI) to see the updated progress of open government in those countries, examine which areas African countries should further improve for sustainable development, and compare the performance of the Open Government Partnership (OGP) member countries to that of non-OGP countries in forming AGOI. This study developed the AGOI with 32 selected countries and four factors (ACC (accountability), TRA (transparency), CPF (citizen participation and freedom) and ICT (information and communication technology)) for the period of 2006–2019. The results show that African countries have continuously increased the values of AGOI for the period. ACC has barely changed, but TRA has increased slightly. Both CPF and ICT have increased at higher growth rates during the period. The OGP group reached much better scores than their non-OGP counterparts, with positive differences in AGOI, ICT, CPF, and TRA, except ACC. The results of this study suggest that the constantly increasing CPF and ICT levels in countries that have similar conditions as African countries should be further improved to function well enough to build accountability and transparency. It is also recommended that countries join the OGP in order to move towards improving government openness and creating sustainable development.