Goffin, who lost to Nick Kyrgios in last year's final, extended his winning streak to nine matches to rise to number eight in the Race to London rankings, boosting his chances of playing in the season-ending tournament.
The 26-year-old was dominant from the start and broke Mannarino to take a 3-1 lead in the opener and maintained the one-break advantage to claim the set, winning 21 of 25 points on his own serve.
Mannarino upsets Cilic, to face Goffin in Japan Open final
World number 31 Mannarino rallied in the second and broke Goffin to take a 4-2 lead but the in-form Belgian responded by breaking the Frenchman immediately and once more in the 11th game as he charged to victory.
David Goffin - ATP TOKYO 2017
Image credit: Getty Images
The win in Tokyo was Goffin's fourth career title and second of the season after his ATP 250 Shenzhen Open triumph last Sunday.
The world number 11 will next travel to China to play in the Shanghai Masters.
Raonic crashes out of Japan Open with new injury
Swiatek's coach praises No. 1 for performances that could 'only be dreamed of'
Share this article