Mobile technologies show great potential to accelerate internet access and usage, especially in developing countries. A better understanding of key drivers and main constraints for mobile internet access is the first prerequisite for governments to design targeted policy solutions. This study exploits a household survey that collects information on information and communications technology access and usage at the household and individual levels in 22 countries in the Global South. The study finds that in addition to infrastructure investment, which has been the main focus of many developing countries, other demand-side factors are of critical importance. Across the developing world, females, the elderly, those who live in rural areas, and those who have a relatively low level of income or education are less likely to adopt mobile internet. Social network effects are found to have a significant positive impact on the usage of mobile internet. Those who have more close friends using an online social network are more likely to adopt mobile internet. Individuals whose five closest friends are using an online social network (such as Facebook or Twitter) are 63.1 percent more likely to adopt it than those without any close friends using such online social network sites/apps. Across regions, although the factors affecting the adoption of mobile internet remain largely the same, the magnitudes of their impacts vary. In Asia, gender differences are negatively associated with mobile internet. In Africa, the impact of education level is more salient than in the other two regions, implying an urgent need to improve digital literacy.