Has secular education contributed to the decline of polygamy in Africa? To answer this question, we study a wave of public school construction in late-colonial Cameroon. Our difference-indifferences and event-study specifications show that school openings have simultaneously increased education and the chances to be in a polygamous union for men and, more surprisingly, for women. We estimate a structural model of marriage to explain why education made women more likely to be in a polygamous union. The main estimated channel is marriage to educated men who are more often polygamists than uneducated men, not direct preferences for polygamy.