Microbiome sequencing has become the standard procedure in the study of new ecological and human-constructed niches. To our knowledge, this is the first report of a metagenome from the water of a greenhouse drain. We found that the greenhouse is not a diverse niche, mainly dominated by Rhizobiales and Rodobacterales. The analysis of the functions encoded in the metagenome showed enrichment of characteristic features of soil and root-associated bacteria such as ABC-transporters and hydrolase enzymes. Additionally, we found antibiotic resistances genes principally for spectinomycin, tetracycline, and aminoglycosides. This study aimed to identify the bacteria and functional gene composition of a greenhouse water drain sample and also provide a genomic resource to search novel proteins from a previously unexplored niche. All the metagenome proteins and their annotations are available to the scientific community via http://microbiomics.ibt.unam.mx/tools/metagreenhouse/.