As world number one, Van Avermaet kicked off the 2018 season with 20th place overall in the Tour of Valencia and 16th overall in the Tour of Oman, in which he won the third stage in a group sprint on the Wadi Dayqah Dam. He proceeded with 50th place in Omloop Het Nieuwsblad, 34th in Strade Bianche, 20th overall in Tirreno–Adriatico, and 17th in Milan–San Remo.
As world number one, Van Avermaet kicked off the 2018 season by finishing 20th overall in the Tour of Valencia and 16th overall in the Tour of Oman. In the latter event, he won the third stage in a group sprint on the Wadi Dayqah Dam. He then secured 50th place in Omloop Het Nieuwsblad, 34th in Strade Bianche, 20th overall in Tirreno–Adriatico, and 17th in Milan–San Remo.