Objective: To determine the emergent literacy and language effects of a low-intensity literacy promotion program (Let’s Read) provided via universal well-child services to parents during the first 4 years of their child’s life. Design: Population-based, cluster randomized controlled trial performed between March 1, 2006, and December 10, 2010. Setting: Maternal and child health centers (clusters) in 5 relatively disadvantaged local government areas in Melbourne, Australia. Participants: All parents attending their 4-week wellchild appointments in participating centers were invited to take part in the study. Intervention: The Let’s Read program was delivered at 4, 12, 18, and 42 months during universal well-child care visits. Main Outcome Measure: Child emergent literacy skills (intrasyllabic, phonemic, and sound/letter knowledge) and language (core, receptive, and expressive), measured at 4 years of age. Results: A total of 630 parents participated, with 365 children in 32 intervention clusters and 265 children in 33 control clusters; 563 children (89.4%) were retained in the study to 4 years of age. The adjusted mean differences (intervention minus control) for emergent literacy was 0.2 (95% CI, −0.2 to 0.6; P=.29) for intrasyllabic units, 0.05 (95% CI, −0.4 to 0.5; P=.85) for phonemic awareness, and 0.1 (95% CI, −1.5 to 1.6; P=.92) for letter knowledge. For language, the differences were 1.6 (95% CI, −1.1 to 4.3; P=.25) for core, 0.8 (95% CI, −2.0 to 3.7; P=.56) for receptive, and 1.4 (95% CI, −1.4 to 4.2; P=.32) for expressive scores. Conclusion: This population-wide primary care literacy promotion and book distribution program provided neither the anticipated benefits to literacy and language nor enhanced uptake of literacy activities at 4 years of age, even when targeted to relatively disadvantaged areas.