Urban environments offer substantial opportunities for wildlife conservation as they commonly overlap the distribution of native species and comprise structurally complex and diverse habitats. Conservation strategies within urban environments currently focus on enhancing or maintaining natural remnant vegetation despite the variety of smaller greenspaces that are known to support wildlife. Residential gardens in particular comprise a major component of the total greenspace in urban areas and offer numerous resources that can be used by multiple taxa, and may therefore represent an important, yet unrealised opportunity for conservation. In this study we aimed to further the understanding of the potential value of gardens for biodiversity conservation by comparing the diversity, presence, abundance and reproductive activity of mammals in gardens to natural urban bushland remnants. We demonstrate that gardens support a similar diversity of native mammals as urban bushland and that the presence, abundance and reproductive activity for most native mammals was similar in both bushland and gardens. With the exception of domestic pets, the presence and abundance of introduced species was not higher in gardens compared to urban bushland. Our study highlights that the potential role of residential gardens for biodiversity conservation should not be overlooked. Given that novel urban ecosystems will continue to expand, inclusion of gardens in wildlife conservation and management actions is likely to greatly increase our ability to conserve wildlife in urban habitats.