Mieres has already enjoyed a sensational career in the Aviva Premiership at Chiefs and has amassed 292 points in just 38 appearances for the Devon club.
The 25-year-old has also enjoyed spells in the Top 14 at Stade Francais and Perpignan, where he was signed as back-up to All Blacks superstar Dan Carter.
Mieres, who can also operate at centre or full back, made his Argentina Test debut in December 2007 against Chile at San Juan and last featured for the Pumas in June last year when he faced France at Cordoba.
Head Coach Richard Hill was delighted to agree terms for Mieres who joins countrymen Leonardo Senatore and Agustin Creevy plus experienced back Paul Warwick in agreeing moves to Warriors next season.
"Ignacio is a superb goal kicker with a very high percentage of success who is very ambitious and keen to join us," said Hill.
"Last season he started the vast majority of games for Exeter as they were very successful and secured a top six finish and with it Heineken Cup rugby.
"He is a tall and athletic outside half who attacks the line with real pace and strength. He will kick goals from everywhere and is a very good all-round player.
"When we have played Exeter we have never looked at the ten channel as a defensive weakness because he is so strong defensively too.
"Ignacio is fluent in English, which is vital for the position he plays, and to get a player of his age and undoubted quality is a very exciting prospect for us."