Background: Adults with intellectual and developmental disabilities (IDD) have high rates of homelessness. This observational study evaluates Bridges to Housing, a cross-sector intervention offering immediate access to housing and supports to this population in Toronto, Canada. Methods: Twenty-six participants, enrolled between April 2016 and December 2017, were assessed at baseline, six and 12 months post-enrolment. Descriptive statistics and generalized linear modelling evaluated quality of life (QOL) and service needs outcomes. Twenty-one service users and providers participated in semi-structured interviews between August 2017 and June 2018 to elicit their experiences of the intervention, which were analysed thematically. Results: Twelve months post-enrolment, 24 participants were successfully housed and reported increased QOL scores (F(2,43) = 13.73, p = <0.001) and decreased perceived unmet service needs (Wald X[superscript 2](2) = 12.93, p = 0.002). Individual-, intervention- and system-level characteristics facilitated housing stability in this population. Conclusions: Cross-sector approaches can improve outcomes for homeless adults with IDD and may have an important role in supporting this marginalized population.