The forward has previously drawn criticism for his off-the-pitch lifestyle and will likely draw more tuts of disapproval when he hosts his party at Parisian nightclub Yoyo on Sunday night. PSG take on Nantes in Ligue 1 action just two days later.
Neymar's teammates and some members of the club's staff are included on the guestlist.
"Sunday is not good (for Neymar's birthday party)," Tuchel said after his squad's 5-0 trouncing of nine-man Montpellier, as quoted by ESPN's Jonathan Johnson. "However, I am neither his father, nor handler, nor agent - I am just his coach.
"I will not say if I am going (to Neymar's party) or not. You can wait until Sunday. It is off-topic.
"Neymar's night is a distraction, obviously, and I always protect my players. I love them lots and prefer to talk internally. If there are hard truths to be said, I prefer to do it internally."
The Brazilian, who turns 28 on Wednesday, confronted match officials in Saturday's 5-0 win after he appeared to disagree with a yellow card he was shown in the opening stanza.
His attacking colleague, Kylian Mbappe, was also in a sour mood when he disagreed with his substitution in the second half. Tuchel said he needed time to decide whether Mbappe would be disciplined for his sulking, according to Goal.