Musiala turns 18 on Friday and marked only his fourth Champions League appearance by slotting home a first-half goal as Bayern routed Lazio 4-1 in Tuesday’s last 16, first leg tie in Rome.
Musiala has dual nationality and, at 17 years, 363 days, became the youngest English or German player to score in the Champions League.
Stuttgart-born Musiala also qualified for England having moved to London as a child and came through the Chelsea academy before joining Bayern in 2019.
He made his England Under-21 debut last November, but has decided to shun The Three Lions and play senior football for Germany.
“At the end, I simply listened to my feelings and this decision feels 100 percent right,” he told broadcaster ARD.
“I have a heart for Germany and a heart for England. Both will continue to beat.
“Germany is the country where I was born and where I started playing football, but I grew up in England and still have many friends there.
“I have thought about this a lot, it was not such an easy decision.”
Having seamlessly replaced veteran Thomas Mueller, who is sidelined by a positive Covid-19 test, Musiala posted “A night to remember” on Twitter alongside pictures of his goal celebration for Bayern on Tuesday.
It is a big week for the attacking midfielder who is due to mark Friday’s milestone birthday by signing a five-year contract with Bayern.
Germany head coach Joachim Loew reportedly wants to select Musiala for the senior squad for next month’s World Cup qualifiers.
A fortnight ago, Germany team director Oliver Bierhoff disclosed having had a “very good” conversation in his bid to persuade Musiala.
There were hints after Bayern’s win in Rome that Musiala will opt for Germany’s seniors having played for their Under-16 national team in 2018.
“I don’t think we have to wait much longer. I would of course be happy if we play for Germany together,” Leon Goretzka, who set up Musiala’s goal in Rome, told Sky.