Loss of green spaces due to urban sprawl is one of the greatest current threats to biodiversity as it leads to habitat fragmentation and loss of native species. Given this scenario, green roofs have been positioned as an alternative technology that allows us to take advantage of the underutilized spaces in city buildings, such as roofs, to generate a habitat for the local flora while providing several environmental, social, and economical benefits. In Mexico City, where 80 % of its surface is covered by buildings and roads, this system was first tested more than twenty years ago. Given the ecosystem importance that has been recognized on this technology in various countries, this study sought to determine the species composition of flora that can be supported in extensive, semi-extensive and intensive green roofs in three sites in Mexico City, as well as evaluate seasonal changes in their communities and determine the causes of variations between sites. To accomplish this, we carried out seasonal censuses for vegetation during 2017 and 2018. As a result, we found 236 species of plants. We found out that the main factors of variation of the diversity between green roofs correspond to the plant taxonomic diversity and to the application of supplementary irrigation during the dry season. These results allow us to conclude that green roofs effectively fulfill the function of being a habitat for plant species in the urban matrix of Mexico City that compensate the loss of green areas.