Nocturne will look to power farm early so he can get level 6. Try to invade him and take away his camps to delay his level 6 power spike.
Nocturne will try to get ahead early by ganking lanes that are immobile or are overextended. Try to track him in his jungle and counter gank lanes that are being ganked. If you cannot counter gank, try to gank a separate lane or steal his camps.
Deep wards inside his jungle or around the entrances to his jungle will help your team spot him before he activates his Ultimate R. Try and get deep vision in his jungle whenever possible.
In the mid-game, avoid splitting up by staying as a team. Nocturne has great pick potential and will try to kill squishy champions who are on their own thanks to his Ultimate R.
Whenever Nocturne is split pushing on the other side of the map, he has no way of getting to his team quickly. If you see him somewhere else, look to engage and start a team fight.
Nocturne will try to take down the squishiest high priority target at the start of the fight. This is usually the Mid or ADC. Clump together in team fights to reduce his one-shot potential.
Nocturne needs to get level 6 as quickly as he can so he can use his Ultimate R to gank lanes. Once he hits this power spike, he will look to actively gank whenever his Ultimate R is up.
Nocturne is a good assassin and will try to kill any isolated target whose out of position in the mid and late game. Avoid letting him pick up free kills by staying as a team.
Delay Nocturne’s level 6 power spike by invading his jungle and stealing away his camps. You can look to invade him if he shows on one side of the map and you’re on the other.