The freshwater Pannus genus comprises cyanobacterial unicellular species with a particular morphology, forming free-floating rounded colonies with thin, homogenous, and colorless colonial mucilage. There is little literature on the taxonomy of the Pannus and none on its metabolism. This study presents the first genomic characterization of a Pannus strain isolated from Pantanal Biome, Brazil. The genome was assembled into 117 contigs with a total size of 5.1 Mb and 99.12% completeness. It contained 4988 protein-encoding genes, including some involved in secondary metabolite biosynthesis, such as cyanobactin and terpenes. Interestingly, P. brasiliensis CCIBt3594 has a complete set of nitrogen fixation genes and is a non-heterocytou unicellular cyanobacterium. Finally, the phylogenomic analyses revealed the lack of information on closely related strains and anchored the genus Pannus within the order Chroococcales, Microcystaceae family, closest to Microcystis spp. representatives. This work presents novel evidence concerning a sparsely characterized genus of the Cyanobacteria phylum and contributes to elucidating taxonomic and systematic issues within the group of unicellular cyanobacteria.