Xylella fastidiosa (Xf), a gram-negative bacterium that causes numerous severe diseases in economically important crops, resides in the host xylem and in the mouthparts of its insect vectors where it produces exopolysaccharides (EPS) and forms robust biofilms. We investigated the role of an endoglucanase (EngXCA2) in Xf subsp. fastidiosa, the causal agent of Pierce’s disease of grapevine, in phenotypes associated with specific stages of biofilm development, surface attachment, and cell-cell aggregation. The ΔengXCA2 mutant strain was significantly compromised in attachment to glass and was unable to develop a complete biofilm relative to the wild-type strain. In addition, ΔengXCA2 mutant was impaired in cell-cell aggregation. Furthermore, ΔengXCA2 mutant produced significantly more EPS than the wild-type strain in vitro. We hypothesize that the endoglucanase, EngXCA2, plays a role in modulating Xf biofilm dynamics by facilitating the turnover of EPS during the biofilm developmental cycle through enzymatic degradation of the predicted β 1,4 glucan backbone of EPS.