The Brazil international was left out of the squad that faced Nimes in Ligue 1 on Friday, and it had been suggested that the attacker had picked up a knock on international duty.
However, Tuchel insisted that the former Santos youngster "doesn't have any issue" and will be involved against United in the European Cup next week.
"Neymar doesn't have any issue. We talked together, like I did with Kylian [Mbappe]. We had an honest discussion and I decided to let him rest today (Friday)," Tuchel told reporters.
"He will be with us tomorrow (Saturday). He will train and get ready for the game against Manchester United. He will be on the pitch, for sure."
Neymar has been in impressive form for the French champions during the 2020-21 campaign, already contributing two goals and one assist in three appearances.
Overall the 28-year-old has netted 72 times and provided 42 assists in 88 outings in all competitions since joining PSG from Barcelona ahead of the 2017-18 campaign.