This paper provides the first causal evidence on how developmental health screenings for young children affect parental behavior, leveraging a quasi-experimental change in South Korea’s National Health Screening Program. Using a difference-in-discontinuities design and administrative data covering 1.3 million screening records, we find that “high-risk” screening results influence a wide range of parental behaviors, with responses varying significantly by household income. Among lower-income families, adverse results lead to greater use of publicly insured medical care, increased disability registration, and delays in subsequent childbirth. In contrast, higher-income families reduce maternal labor supply and are more likely to relocate, suggesting costly private adjustments to secure additional caregiving time and access to private developmental rehabilitation facilities. These findings highlight how household resources shape both the capacity and nature of parental responses to early health information.