Manager Joachim Low named an unchanged XI from the side that dispatched Iceland 3-0 last week.
The visitors started the game on the front foot and Emre Can fashioned the first chance of the game inside the opening five minutes. The Dortmund man, however, blazed his effort over the bar.
Both sides went close soon after, with Kai Havertz and Valentin Mihaila both nearly finding the back of the net.
Germany broke the deadlock in the 17th minute. A quick break saw Havertz race behind the Romania defense and he showed great awareness to cut the ball back for Gnabry to tap into the net.
Joshua Kimmich saw him thunderous effort from distance hit the crossbar two minutes later and Gnabry's shot from the rebound was well-saved by Florin Nita.
Germany continued to dominate proceedings for the rest of the first half but could not add a second goal before the break.
The second half continued in the same fashion but an inspired Nita in the Romania goal thwarted all the efforts that came his way.
Timo Werner was introduced for Chelsea teammate Kai Havertz in the 77th minute and he had two good chances to score late in the game but failed to take either.
The in-form Nicolae Stanciu had a great chance to level the scores in injury time but he dragged his shot wide when placed one-on-one with Manuel Neuer. The 27-year-old should unarguably have done better.
Germany held on for the win, which takes them joint-top of Group J in UEFA's section of the 2022 FIFA World Cup qualifiers.
Here are five talking points from the fixture.
#5 Insipired Florin Nita stands tall against Germany
Despite ending on the losing side, Romania's goalkeeper Florin Nita ended the game as arguably the standout player from the fixture.
The 33-year-old came up against some of the best players in the world but was unfazed by the task before him and discharged his duties with aplomb.
In many ways, Nita was what stood in the way of an embarrassing defeat for his side, with several fine saves keeping his side in the game.
In total, the Sparta Prague man made eight saves, with his standout stops coming from Timo Werner and Serge Gnabry.
His saves kept Romania in the game when they should have already been blown away and the hosts had a last-gasp chance to level matters but failed to take it.
#4 International football offering succour for Kai Havertz
Kai Havertz has not enjoyed the best of starts to his Chelsea career following his club-record transfer from Bayer Leverkusen last summer.
The 21-year-old has contributed just five goals from 31 matches in all competitions for the Blues, which is hardly the return that was expected upon his arrival.
This has consequently seen Havertz lose his spot in the starting lineup on the club scene but he remains an integral player for Joachim Low and Germany.
He has so far started both games in the World Cup qualifier for the four-time world champions and has made attacking contributions in both games.
Having scored Germany's second goal in the 3-0 victory over Iceland, Havertz provided the assist for Gnabry to score the winner against Bulgaria.
This means he has had more attacking contributions in two games for Germany than he has in his last six Premier League games for the Blues. Chelsea fans will be hoping that his form on the international scene can be carried over to Stamford Bridge.