The 21-year-old midfielder has been on loan with Millers since the summer and will now remain at New York Stadium for the rest of the season.
Ward has also committed himself to Spurs until the summer of 2018 as he looks to continue his development in the Championship.
.@GrantWard_ has signed a new contract until 2018. His loan at Rotherham is extended until the end of the season. pic.twitter.com/mO0yQWFM6p
— Tottenham Hotspur (@SpursOfficial) February 1, 2016