Large numbers of infants and toddlers have parents who live apart due to separation, divorce, or nonmarital/noncohabiting childbearing, yet this important topic, especially the controversial issue of frequent overnights with nonresidential parents, is understudied. The authors analyzed data from the Fragile Families and Child Wellbeing Study, a longitudinal investigation of children born to primarily low-income, racial/ethnic minority parents that is representative of 20 U.S. cities with populations over 200,000. Among young children whose parents lived apart, 6.9% of infants (birth to age 1) and 5.3% of toddlers (ages 1 to 3) spent an average of at least 1 overnight per week with their nonresident parent. An additional 6.8% of toddlers spent 35%–70% of overnights with nonresident parents. Frequent overnights were significantly associated with attachment insecurity among infants, but the relationship was less clear for toddlers. Attachment insecurity predicted adjustment problems at ages 3 and 5, but frequent overnights were not directly linked with adjustment problems at older ages.