Importance Although neighborhoods are thought to be an important health determinant, evidence for the relationship between neighborhood poverty and health care use is limited, as prior studies have largely used observational data without an experimental design. Objective To examine whether housing policies that reduce exposure to high-poverty neighborhoods were associated with differences in long-term hospital use among adults and children. Design, Setting, and Participants Exploratory analysis of the Moving to Opportunity for Fair Housing Demonstration Program, a randomized social experiment conducted in 5 US cities. From 1994 to 1998, 4604 families in public housing were randomized to 1 of 3 groups: a control condition, a traditional Section 8 voucher toward rental costs in the private market, or a voucher that could only be used in low-poverty neighborhoods. Participants were linked to all-payer hospital discharge data (1995 through 2014 or 2015) and Medicaid data (1999 through 2009). The final follow-up date ranged from 11 to 21 years after randomization. Exposures Receipt of a traditional or low-poverty voucher vs control group. Main Outcomes and Measures Rates of hospitalizations and hospital days, and hospital spending. Results Among 4602 eligible individuals randomized as adults, 4072 (88.5%) were linked to health data (mean age, 33 years [SD, 9.0 years]; 98% female; median follow-up, 11 years). There were no significant differences in primary outcomes among adults randomized to receive a voucher compared with the control group (unadjusted hospitalization rate, 14.0 vs 14.7 per 100 person-years, adjusted incidence rate ratio [IRR], 0.95 [95% CI, 0.84-1.08;P = .45]; hospital days, 62.8 vs 67.0 per 100 person-years; IRR, 0.93 [95% CI, 0.77-1.13;P = .46]; yearly spending, $2075 vs $1977; adjusted difference, −$129 [95% CI, −$497 to $239;P = .49]). Among 11 290 eligible individuals randomized as children, 9118 (80.8%) were linked to health data (mean age, 8 years [SD, 4.6 years]; 49% female; median follow-up, 11 years). Receipt of a housing voucher during childhood was significantly associated with lower hospitalization rates (6.3 vs 7.3 per 100 person-years; IRR, 0.85 [95% CI, 0.73-0.99;P = .03]) and yearly inpatient spending ($633 vs $785; adjusted difference, −$143 [95% CI, −$256 to −$31;P = .01]) and no significant difference in hospital days (25.7 vs 28.8 per 100 person-years; IRR, 0.92 [95% CI, 0.77-1.11;P = .41]). Conclusions and Relevance In this exploratory analysis of a randomized housing voucher intervention, adults who received a housing voucher did not experience significant differences in hospital use or spending. Receipt of a voucher during childhood was significantly associated with lower rates of hospitalization and less inpatient spending during long-term follow-up.