Institutional quality has been increasingly identified as crucial for economic development. In line with previous work which has explored the determinants of good institutions, this paper examines the impact of economic and social inequalities between ethnic groups on government quality. I hypothesize that greater inequalities between groups will tend to undermine institutions both because they tend to legitimize corruption in the eyes of disadvantaged groups and because of the efforts of better-off groups to maintain their privileges. Based on a panel of 29 developing countries, I find that socio-economic ethnic group inequalities reduce government quality, something which suggests the convenience of policies that can level the playing field in ethnically heterogeneous societies.