The Argentine carded a bogey-free round of 65, the day's best, to sign off at 17 under par, one better than Thomas Detry(66) and overnight leaders Sergio Garcia (69) and Richard Bland (69).
It was Romero's second European Tour title, ten years after he won the Deutsche Bank Players Championship of Europe.
''This is a moment that changes my life,'' the 36-year-old said.
Detry had been leading but the Belgian could only watch as Romero finished with his seventh birdie on Munich's Eichenried course.
Garcia's hopes took a hit with his second bogey on the 16th hole, while Bland had his second bogey on the 17th. Both ended with birdies but it wasn't enough to force a playoff.
Rikard Karlberg (66) finished fifth at 14 under, one stroke ahead of Tommy Fleetwood, who finished with an eagle for a 67, and Renato Paratore (68).