Introduction: Unmet social needs are linked with greater healthcare utilization, but most studies lack timely and granular data on these needs. The 2-1-1 helpline is a telephone helpline focused on social needs. The objective of the study is to determine whether the number of 2-1-1 requests per 1,000 people is associated with preventable emergency department visits and compare the strength of the association with another commonly used predictor, Area Deprivation Index. Methods: This cross-sectional study linked 2-1-1 requests to emergency department visits from uninsured and Medicaid-insured patients by ZIP code for a large urban hospital system from January 1, 2016 to August 31, 2019. Negative binomial regression analysis was used to estimate the association of 2-1-1 service requests and Area Deprivation Index with preventable emergency department visits. Results: A total of 233,146 preventable emergency department visits and 520,308 2-1-1 requests were analyzed. For every 1-SD increase in 2-1-1 requests per 1,000 population, preventable emergency department visits increased by a factor of 3.05, even after controlling for local area deprivation and other population characteristics (p<0.001). Conclusions: Requests to 2-1-1 helplines are strongly associated with preventable emergency department visits. This information may help hospital leaders and policymakers target social needs interventions to the neighborhoods with the greatest need.