The 43-year-old Vilanova, who underwent surgery on a tumour in his glands last November, stepped up from his role as assistant coach to replace Pep Guardiola as first-team coach for this season.
The La Liga leaders put out a statement cancelling a Christmas event planned with local media and president Sandro Rosell earlier in the morning, saying the reasons would be given later.
"Very sorry to hear the news," Barca midfielder Xavi said on his official Twitter account.
(Reporting by Mark Elkington, editing by Ed Osmond)
- Sports & Recreation
- Pep Guardiola
- Sandro Rosell