The striker played half-an-hour for Germany Under-21s in their 2-1 win over England at Bournemouth on Tuesday evening.
Nmecha has chosen to switch allegiance to Germany having played at six age levels for England.
However, clearance for him to make the change only came through just before kick-off at the Vitality Stadium.
He had not been able to play in Germany’s previous game against France last Thursday, although the Manchester City frontman had trained with them.
Nmecha, 20, said: “I chose Germany, where I was born, I’ve been thinking a long time about what I really want.
“This was the right decision, and it’s final. I learned 10 minutes before the game that I was allowed to play.”
Born in Hamburg, Nmecha moved to Manchester with his family when he was nine.
He joined Manchester City’s academy after a short time being in the country and rose through their youth ranks.
Nmecha played for England from Under-16s to Under-21s level.
He was in the England squad which won the Toulon Tournament last year.
Nmecha hopes to play for Germany in the European Under-2s1 Championship which is being held in Italy and San Marino this summer.
His younger brother Felix is also at City.
With international duty now over, Nmecha will turn his attention to North End’s push for the play-offs.
He will link up with Alex Neil’s squad on Thursday at Springfields to prepare for Saturday’s visit to Reading.
Nmecha has started the last three North End games, mainly playing on the wing.
However, the bulk of his 36 appearances for PNE have come as a striker and it was in a central position where he played for Germany.