Despite increasing interest in the role of parks on children’s health, there has been little empirical research on the impact of park interventions. We used a quasi-experimental pre-post study design with matched controls to evaluate the effects of park redesign and renovation on children’s quality of life (QoL) in underserved neighborhoods in New York City, with predominantly Hispanic and Black populations. Utilizing longitudinal data from the Physical Activity and Redesigned Community Spaces (PARCS) Study, we examined the parent-reported QoL of 201 children aged 3–11 years living within a 0.3-mile radius of 13 renovated parks compared to 197 children living near 11 control parks before and after the park intervention. QoL was measured using a modified version of the KINDL questionnaire, a health-related QoL scale that assessed children’s physical and emotional well-being, self-esteem, and well-being in home, peer, and school functioning. Linear mixed regression model was used to examine the difference in difference (DID) between the intervention vs. control group for QoL. We found a significant differential improvement in the physical well-being subscale of KINDL in the intervention vs. control group (DID = 6.35, 95% Confidence Interval [CI] = 0.85-11,85, p = 0.024). The effect was particularly strong among girls (DID = 7.88, p = 0.023) and children of the lowest socio-economic background (p < 0.05). No significant DID was found in other KINDL domains. Our study indicated a beneficial impact of improving park quality on the physical well-being of children residing in underserved neighborhoods. These findings lend support for investments in neighborhood parks to advance health equity.