Brett Smitheram from Chingford defeated fellow Briton Mark Nyman in three straight rounds during the contest's final in the French city of Lille.
The 37-year-old's highest scoring word was BRACONID, meaning a parasitic wasp, which earned him 176 points.
Mr Smitheram, who also collected a 7,000 euro (Â£5,873) prize, said he was "absolutely thrilled to have won".
It was the former UK champion's first victory at the tournament. His best previous result was reaching the quarter finals in 2014.
His Knutsford-based opponent, Mark Nyman, is a writer who was named world Scrabble champion in 1993 and has been a producer on legendary Channel 4 word game Countdown.
After his win, Mr Smitheram admitted his opponent was one of his "Scrabble idols" when he was growing up.
"He used to be the producer of Countdown and he got me on Countdown when I was 17, 20 years ago now. I was on Countdown about 10 or 12 times," the new champion said.
"So he's known me for 20 years, and at the time when he interviewed me for Countdown he said 'What's your biggest aspiration?' and I said 'I want to win the Scrabble World Championship'.
"And today I beat him in order to do it. Quite a story behind it."
A recruitment consultant from east London has fought off other wordsmiths to be crowned Scrabble World Champion.