Influenza viruses are highly capable of mutating and adapting in mammalian hosts. While these viruses have been extensively studied in birds, research on their presence in bats has been limited. However, influenza viruses circulating in bats have shown notable molecular divergence. The present study aimed to characterize the phylogenetic, evolutionary, and antigenic relationships of an influenza A virus detected in the fishing bat Noctilio albiventris. As part of a pathogen surveillance study of public health interest, 159 rectal samples were collected from bats in the Colombian Caribbean. The samples were sequenced using RNA-Seq. A genome (eight viral contigs) associated with the Orthomyxoviridae family was identified in a pool. Most segments showed approximately 90% similarity with H18N11, except for the neuraminidase. Analysis of the N protein shows that occupies a basal position relative to the N11 subtype, with its divergence date estimated to be approximately 50 years earlier than the earliest reported N11 sequence. 3D modeling identified three mutations (K363R, T242K, and I139V), which may enhance interaction with the HLA-DR of bats. The analyses and antigenic divergence observed in the N protein of N. albiventris suggests the existence of a new subtype (H18N12) with unknown pathogenicity, which requires further investigation.