This study empirically tested 3 mechanisms commonly suggested to disadvantage youths whose mothers are incarcerated in prison. An event history analysis of school dropout was conducted on a sample of 6,008 adolescents in a large city created by merging several Illinois state administrative data. Findings revealed that adolescents are indeed at greater risk of school dropout during the year(s) their mothers are incarcerated. Children who are removed from maternal guardianship and placed under the guardianship of a relative adult are observed to have higher odds of school dropout than children who remain under maternal guardianship after the mother's imprisonment. Lastly, attending a school in which maternal imprisonment is fairly common is not found to place adolescents at greater risk of school dropout after controlling for school quality.