We developed and tested MivacunaLA/MyshotLA, a community-informed mobile phone intervention, to increase COVID-19 vaccination among Latino parents/caretakers of minors in under-resourced areas of Los Angeles by addressing misinformation and building trust. We recruited Latino parents/caregivers with at least one unvaccinated child in East and South Los Angeles in the summer of 2021 and evaluated MivacunaLA as a randomized controlled trial with a wait-list control group. A difference-in-difference analysis showed Latino parents/caregivers that participated in MivacunaLA (n = 246), in comparison to the control group, were 15 percentage points more likely (p = 0.04) to report vaccination of minors aged 12–17 years, and 12 percentage points more likely (p = 0.03) to report a positive intention to vaccinate minors aged 2–11 years (when COVID-19 vaccines became available). Mobile phone-delivered digital interventions using videos and culturally tailored educational material to promote COVID-19 vaccine confidence can be an effective way to combat misinformation and deliver timely information to marginalized communities. Community-based participatory research approaches are crucial to advance health equity among minority communities, especially immigrant Spanish-speaking underserved communities.