The South African midfielder enjoyed a loan spell with the Toffees last season, and a 4.5 million pound fee has been agreed to make the move permanent
Pienaar has been eyeing a return to the Toffees for much of the summer and Goal.com reported earlier in the week that a deal between the two sides was close, with the 30-year-old having agreed personal terms.
The South African enjoyed a loan spell back at Goodison Park last season where he had previously played between 2007 and January 2011 before moving to north London.
Pienaar struggled to break into the side under Harry Redknapp after moving for 2.5 million pounds, and struggled with injuries that restricted him to making just 18 appearances in 12 months at White Hart Lane.
After switching temporarily to the Toffees in January, Pienaar made 14 appearances, notching four goals in the process, including a stunning equalizer in Everton's 4-4 draw with Manchester United at Old Trafford.
The former Ajax man has scored 16 goals in total in 147 appearances for the Toffees in three spells.
Everton has also bolstered its attack with the signing of Steven Naismith this summer, although Tim Cahill has departed Goodison after eight seasons, moving to New York Red Bulls.
Spurs new manager Andre Villas-Boas has added to his midfield ranks already this summer, snapping up Gylfi Sigurdsson from Hoffenheim, but the club faces a battle to keep hold of Luka Modric, who is eyeing a move to Real Madrid.