Pedro completed his transfer to Watford last month after the deal was originally arranged in October, and uploaded a picture of him kissing Maia on London's Southwark Bridge a week ago.
Watford's new signing Joao Pedro is dating 15-year-old Brazilian TV star Mel Maia.
Pedro, 18, completed his move to the Hornets at the start of the January window, and has since been settling into life in England.
And the forward was paid a visit by his girlfriend just last week, with Pedro then uploading a picture to Instagram of them kissing on Southwark Bridge.
The legal age of consent in the UK is 16, compared with 14 in their native Brazil.
A Watford spokesman told the Star: "Both Joao and his girlfriend are acutely aware of both the legality and cultural differences between the UK and Brazil.
"She has flown back to Brazil, will remain resident there and has no intention of returning to England until after her 16th birthday.”
The pair have been in a relationship since September - the same month as Pedro's birthday, while Maia does not turn 16 until May.
Maia shot to fame in 2012 as Rita in hit TV soap Avenida Brasil, earning her multiple awards.
She then starred as the main role of Perola in the drama Joia Rara.
In a separate post on Instagram almost two months ago, Pedro uploaded another picture with Maia, along with the caption: "My heart is yours."
While in another he said: "You complete me."
Maia put her own picture up alongside Pedro, which said: "Thank you 2k19 [2019] for giving me the best gift."
Pedro's move to Watford has been a few months in the offing, after the Hornets agreed terms with Fluminense back in October.
Watford paid out £3.6million to acquire his services on a five-year contract.
He made his debut as a substitute in the FA Cup clash with Tranmere on January 4, with his first start coming in the replay defeat.
Boss Nigel Pearson said on his arrival: "It's important for him to settle in and it's important we don't heap too much pressure on a player of such young years.
"We know he is keen to get started and I'm sure he'll get a warm welcome and get support from the players and the club."
Trevorn
408
When I was 15 I was still trying to balance the light switch between on and off😂😂😂😂Now look these kids are getting in serious relationships.
vakdryz
19
In my country dating a girl Bellow 18 is the biggest mistake, you must be arrested and Jailed 30 years