After managing Vicenza, Guidolin accepted the head coach position at Serie A side Udinese for the 1998–99 season. Their previous third-place finish had qualified them the first round of the 1998–99 UEFA Cup, but they did not progress beyond this stage, losing to Bayer Leverkusen. In the remaining league campaign, Guidolin was only able to guide them to a mid-table finish and was fired only days before the start of the following season.