The Welshman will feature in TV adverts and appear as a guest on BT's new sports channel, which recently won the rights to broadcast a number of top-flight fixtures.
The news suggests that Bale could remain a Premier League player beyond the end of this season, despite speculation constantly linking the Welshman with a move to abroad.
Manchester United could still be a destination for the 23-year-old but they were left stunned by Tottenham's £70m asking price, as Goal.com revealed earlier this year.
The Spurs winger has also attracted interest from Real Madrid, who remain favourites to sign him, with Bale himself expressing his admiration for the club and an interest in playing abroad.
Tottenham, though, are increasingly confident of retaining Bale and are set to offer him a bumper new five-year contract should they secure Champions League football.
|REAL MADRID BOUND?|
|11/8||Gareth Bale is 11/8 with Paddy Power to make Real Madrid his next permanent home|
"I am delighted to continue my relationship with BT by becoming a BT Ambassador. I feel honoured to join an exciting band of inspirational sporting figures, which has included Olympic heroes like the Brownlee brothers and Paralympic gold medallist Jonnie Peacock," Bale said.
The Tottenham midfielder has scored 21 goals in 36 games for Andre Villas-Boas' side this season and is among the frontrunners for the Player of the Year awards.