Mobile phones have made a significant impact on developing countries, which have played a key role in the mobile phone global value chain (GVC). The dynamic of the GVC, notably growing concentration in trade and production and the rise of low-end markets, is shaping the impact of economic upgrading on social upgrading. Increased GVC concentration has limited employment growth to just a few countries and firms, and the prevalence of casual labor has led to segmented upgrading among workers. Moreover, the low-end market is vulnerable to poor working conditions. However, shifting end markets are presenting new opportunities for social upgrading in developing countries.