Human papillomavirus (HPV) vaccine series completion among adolescent Hispanic males (35%) is lower than the Healthy People 2020 80% goal. This directed qualitative content analysis identified mothers' beliefs about their sons completing the series. We found that mothers (N = 19) (1) express positive feelings; (2) believe the vaccine has positive effects; (3) identify the father and doctors as supporters and friends as nonsupporters; (4) list health insurance, transportation, and clinic reminders as facilitators; and (5) mention affordability as a barrier to vaccine completion. Results provide guidance for interventions. Increasing HPV vaccination among boys will decrease the overall incidence of HPV in this population.