This prospective, longitudinal study examined associations between whether and when children first acquire a mobile phone and their adjustment measures, among low-income Latinx children. Children (N = 263; 55% female; baseline M[subscript age] = 9.5) and their parents were assessed annually for 5 years from 2012. Children first acquired a mobile phone at a mean (SD) age of 11.62 (1.41) years. Pre-registered multilevel models tested associations linking phone ownership, phone acquisition age, and the interaction between ownership and acquisition age to levels and changing trends of depressive symptoms, school grades, and reported and objectively assessed sleep. Results showed no statistically significant associations, controlling the False Discovery Rate. Findings suggest an absence of meaningful links from mobile phone ownership and acquisition age to child adjustment.