Early reading literacy develops through repeated access to print, responsive adult interaction, and meaningful opportunities to engage with books. In resource-constrained communities, mobile libraries may extend these opportunities beyond the classroom and home. This cross-sectional study examined the association between the quality of mobile library services and early reading literacy among children aged 5–6 years in an anonymized local study area. The sample comprised 150 children from five early childhood education institutions and 150 parents or caregivers; all participating children had prior exposure to the mobile library program. Consequently, the study estimates associations within an exposed sample and does not compare children with and without access to mobile library services. Data were collected from September to December 2025 using a structured parent/caregiver questionnaire and an early reading literacy assessment. Mobile library services were represented by visit frequency, access to age-appropriate books, participation in shared reading, and parental involvement, whereas early reading literacy covered letter recognition, phonological awareness, basic vocabulary, and simple comprehension. Simple linear regression showed a positive association between the overall mobile library service score and early reading literacy (B = 0.55, β = 0.41, t = 5.90, p < 0.001, R² = 0.17). The four service dimensions also showed positive unadjusted standardized associations (β = 0.22–0.31; all p < 0.05), but these indicator-level estimates were not adjusted for parental education or the number of children’s books at home and should not be interpreted as independent causal effects. The findings therefore support an association between service quality and literacy within the five participating institutions, while causal effects and comparisons with unexposed children require longitudinal or quasi-experimental evaluation.