Tannerella forsythia is a Gram-negative oral anaerobe implicated in the development of periodontitis, a chronic inflammatory disease induced by bacterial infections which leads to tooth loss if untreated. Since biofilms formed by periodontal bacteria are considered important in disease progression and pose difficulties in treatment, we sought to investigate the underlying mechanisms of T. forsythia biofilm formation. This was carried out by screening random insertion mutants of T. forsythia for alterations in biofilm development. This approach lead to the identification of an operon involved in exopolysaccharide (EPS) synthesis. An isogenic mutant of one of the genes, wecC, contained within the operon was constructed. The isogenic wecC mutant showed increased ability to form biofilms as compared to the parent strain. The wecC mutant also formed aggregated microcolonies and showed increased cell-surface associated hydrophobicity as compared to the parent strain. Moreover, biochemical characterization of the wecC mutant indicated that glycosylation of surface glycoproteins was reduced. Therefore, our results suggest that the wecC operon is associated with glycosylation of surface-glycoprotein expression and likely plays an inhibitory role in T. forsythia biofilm formation.