Context: It is unknown whether rural isolation may affect birth outcomes and infant mortality differentially for Indigenous versus non-Indigenous populations. We assessed birth outcomes and infant mortality by the degree of rural isolation among First Nations (North American Indians) and non-First Nations populations in Manitoba, Canada, a setting with universal health insurance. Methods: A geocoding-based birth cohort study of 25,143 First Nations and 125,729 non-First Nations live births to Manitoban residents, 1991-2000. Degree of rural isolation was defined by an indicator of urban influence (no, weak, moderate/strong) based on the percentage of the workforce commuting to urban areas. Findings: Preterm birth and low birth weight rates were somewhat lower in all rural areas regardless of the degree of isolation as compared to urban areas for both First Nations and non-First Nations. Infant mortality rates were not significantly different across areas for First Nations (10.7, 9.9, 7.9, and 9.7 per 1,000 in rural areas with no, weak, moderate/strong urban influence, and urban areas, respectively), but rates were significantly lower in less isolated areas for non-First Nations (7.4, 6.0, 5.6, and 4.6 per 1,000, respectively). Adjusted odds ratios showed similar patterns. Conclusions: Living in less isolated areas was associated with lower infant mortality only among non-First Nations. First Nations infants do not seem to have similarly benefited from the better health care facilities in urban centers, suggesting a need to improve urban First Nations' infant care in meeting the challenges of increasing urban migration.