During the third and final ascent of the Mur de Huy at La Flèche Wallonne, Alaphilippe accelerated near its summit, overtaking the sole race leader Jelle Vanendert in the last 100 metres of the race and dropping him.
Alejandro Valverde, who had won the last four La Flèche Wallonne editions, staged a late fight-back and almost caught Alaphilippe, but the latter was able to kick again in the final metres to increase his lead over Valverde and eventually win the race.
It was the biggest victory of Alaphilippe's career at that point, and he was the first French winner of La Flèche Wallonne since Laurent Jalabert won in 1997.

Alaphilippe participated in his second Tour de France, and claimed his maiden Tour de France stage win in stage 10 with a series of attacks and aggressive descending in the Alps.
He took the maximum mountains classification points on the Montée du plateau des Glières,  the Col de Romme and the Col de la Colombière, finishing the stage 1 minute, 34 seconds ahead of the second placed rider Ion Izagirre of Bahrain–Merida, and 3 minutes, 23 seconds ahead of the peloton that included the defending champion Chris Froome.
Alaphilippe also took the lead in the mountains classification after the end of Stage 10.
Alaphilippe won the 16th stage of the race after Adam Yates crashed, while leading, on the descent 7 kilometres (4.3 miles) before the finishing line.

The following month, Alaphilippe won the Clásica de San Sebastián, out-sprinting Bauke Mollema for the win, after the two riders escaped the field on the final climb.
He then won the third stage and the general classification of the Tour of Britain, after taking the overall lead on the sixth stage of the week long competition.
Alaphilippe continued to have success in stage races, as he won the Okolo Slovenska less than a week later.

Despite his large amount of successes in 2018, Alaphilippe faced disappointment at the UCI Road World Championships, where he was appointed France's team leader.
On the final climb, he cracked and lost contact with the race leaders, and ended up finishing 8th.
During the third and final ascent of the Mur de Huy at La Flèche Wallonne, Alaphilippe accelerated near its summit, overtaking the sole race leader Jelle Vanendert in the last 100 metres of the race and dropping him. Alejandro Valverde, who had won the last four La Flèche Wallonne editions, staged a late fight-back and almost caught Alaphilippe, but the latter was able to kick again in the final metres to increase his lead over Valverde and eventually win the race. It was the biggest victory of Alaphilippe's career at that point, and he was the first French winner of La Flèche Wallonne since Laurent Jalabert won in 1997.
Alaphilippe participated in his second Tour de France, and claimed his maiden Tour de France stage win in stage 10 with a series of attacks and aggressive descending in the Alps. He took the maximum mountains classification points on the Montée du plateau des Glières,  the Col de Romme and the Col de la Colombière, finishing the stage 1 minute, 34 seconds ahead of the second placed rider Ion Izagirre of Bahrain–Merida, and 3 minutes, 23 seconds ahead of the peloton that included the defending champion Chris Froome. Alaphilippe also took the lead in the mountains classification after the end of Stage 10. Alaphilippe won the 16th stage of the race after Adam Yates crashed, while leading, on the descent 7 kilometres (4.3 miles) before the finishing line.
The following month, Alaphilippe won the Clásica de San Sebastián, out-sprinting Bauke Mollema for the win, after the two riders escaped the field on the final climb. He then won the third stage and the general classification of the Tour of Britain, after taking the overall lead on the sixth stage of the week long competition. Alaphilippe continued to have success in stage races, as he won the Okolo Slovenska less than a week later.
Despite his large amount of successes in 2018, Alaphilippe faced disappointment at the UCI Road World Championships, where he was appointed France's team leader. On the final climb, he cracked and lost contact with the race leaders, and ended up finishing 8th.
Julian Alaphilippe