Waghorn, 27, who has put pen to paper on a two-year deal, follows former Rangers team-mate Joe Garner to Portman Road.
“Mick McCarthy adds firepower to his striking options with the signing of Martyn Waghorn from Rangers, paying a substantial fee to land the forward,” Ipswich said on their official website.
“The former Leicester man has passed a medical and penned his contract and will be hoping to make his debut for the Blues in the Carabao Cup away to Luton (on Tuesday).”
Waghorn made eight appearances for hometown club Sunderland after progressing through their academy and joined Leicester in a £3million deal in 2010.
He had loan spells at Hull, Millwall and Wigan before moving north to Rangers on a free transfer in 2015 and scored 41 goals in a total of 78 appearances.
Waghorn partnered Garner up front for the Scottish side last season, with Ipswich signing the latter for an undisclosed fee in June.