Vergne, who has driven for the Italian team since graduating to F1 racing via the Red Bull young driver programme in 2012, made the announcement on Twitter.
“Despite a good season and 22 points, I'll not drive anymore for Toro Rosso in 2015,” said the Frenchman. “Thanks for those years. Let's go for another big challenge.”
Vergne, 24, has finished 17th, 15th and 13th overall in his three seasons to date. He was outqualified 12-7 by rookie team mate Daniil Kvyat in 2014, but finished the year with 14 points more than the Russian.
Carlos Sainz Junior, the recently-crowned Formula Renault 3.5 champion and another Red Bull junior driver, is one of the favourites to replace Vergne at Toro Rosso, having tested for Red Bull at this week’s test in Abu Dhabi.
Kvyat, meanwhile, will partner Daniel Ricciardo at Red Bull from 2015.