In the picture, which appears to be taken in her Porsche, the 65-year-old wears sunglasses and has her hair styled in a simple blowout.
"No #SocialMediaQueen can be crowned without posting a selfie, so here's my first!" she wrote as the caption, including a link to the voting page for the award.
Jenner, who currently stars in her own docuseries, I Am Cait, was nominated for the social media queen award. She Tweeted about the nod a week ago, writing, "And to think I wouldn't have qualified for this nom a few months ago…What an honor!"
RELATED VIDEO: Caitlyn Jenner's Message to Transgender Youth: 'We Are All Beautiful'
Also nominated for the award are A-list celebs Taylor Swift, Katy Perry, Miley Cyrus, Nicki Minaj and Selena Gomez.
Jenner joined Twitter in June and quickly broke a record, gaining more than 1 million followers in just hours.