The 19-year-old beat Aylin Bayramoglu and Ali Stroker to win a seven-episode arc on the upcoming season of Glee in last night's season finale.
Jenner chose to perform Edward McCain's 'I'll Be' for his last-chance performance, and also read a poem listing the reasons he would be good for Glee.
After Glee's executive producer Ryan Murphy announced that Jenner had won, he said: "This is the greatest moment of my life. I won The Glee Project and I could not be happier and more grateful.
"I'm never going to take this for granted. I'm never going to change. I'm going to be who I am every single step of the way and I'm so excited."
He also tweeted: "Thank you to everyone for their love and support throughout this ENTIRE journey I will be grateful and thankful to you all FOREVER I PROMISE."
Meanwhile, last year's winner Damian McGinty congratulated Jenner, tweeting: "Very proud of my man @Blake_Jenner winning The Glee Project. Ive got to know this guy (secretly) the past while,and he is awesome. #truestar".
Elsewhere, Murphy used his Twitter page to drop some hints about Jenner's part in Glee, saying: "Writing such a great role for the winner! And just wait until you see who they are dating..."
He also hinted that some of the runners-up could appear in Glee as well, writing: "Fan: 'I want Aylin on GLEE'. Me: 'Me too.'"
Glee will return for its third season on September 13 on Fox.