The Gram-negative bacterium Gallibacterium anatis is a recently recognized, yet major, cause of salpingitis and peritonitis in egg-laying chickens, leading to decreased egg-production and animal welfare issues worldwide. Insight into the pathogenesis of disease and knowledge of important virulence factors is urgently required to combat high levels of drug resistance and antigenic diversity. Recently, varying numbers of loci encoding putative F17-like fimbriae were identified in the genomes of G. anatis. The objective of this study was to investigate the basic characteristics of the F17-like putative fimbrial protein precursor GalF-A and its immunogenic potential. In vitro expression and surface-exposure of GalF-A was demonstrated by flow cytometry and immunofluorescence microscopy, and the predicted function of GalF-A as a F17-like fimbrial subunit was confirmed by immunogold electron microscopy. A fimbrial knock-out mutant was generated and used to confirm the in vitro results. Importantly, the mutant was significantly attenuated, as compared to the wild-type, following intraperitoneal challenge of the natural host, the chicken. Finally, in vivo immunization with GalF-A in chickens demonstrated an 80% protection rate, thus a clear immunogenic potential. In conclusion, we describe the first fimbrial protein precursor from G. anatis and demonstrate its potential as a future vaccine candidate.