OBJECTIVES: We conducted 2 studies to determine the impact of text message immunization reminder-recalls in an urban, low-income population. METHODS: In 1 study, text message immunization reminders were sent to a random sample of parents (n = 195) whose children aged 11 to 18 years needed either or both meningococcal (MCV4) and tetanus-diphtheria-acellular pertussis (Tdap) immunizations. We compared receipt of MCV4 or Tdap at 4, 12, and 24 weeks with age- and gender-matched controls. In the other study, we compared attendance at a postshortage Haemophilus influenzae B (Hib) immunization recall session between parents who received text message and paper-mailed reminders (n = 87) and those who only received paper-mailed reminders (n = 87). RESULTS: Significantly more adolescents with intervention parents received either or both MCV4 and Tdap at weeks 4 (15.4% vs 4.2%; P < .001), 12 (26.7% vs 13.9%; P < .005), and 24 (36.4% vs 18.1%; P < .001). Significantly more parents who received both Hib reminders attended a recall session compared with parents who only received a mailed reminder (21.8% vs 9.2%; P < .05). After controlling for age, gender, race/ethnicity, insurance status, and language, text messaging was still significantly associated with both studies' outcomes. CONCLUSIONS: Text messaging for reminder-recalls improved immunization coverage in a low-income, urban population.