Walcott, who has scored 76 goals in 302 appearances since joining Arsenal from Southampton in 2006, has signed a four-year deal having had just one year left on his old contract at the Emirates.
The 26-year-old was a peripheral figure for much of last season, but ended the campaign in style with a hat-trick in the 4-1 final-day win over West Brom before scoring in the 4-0 FA Cup final victory over Aston Villa.
Cazorla, 30, enjoyed a fine year for Arsene Wenger’s side last year, making 53 appearances in a deeper midfield role.
He has made 148 appearances since his arrival from Malaga in 2012, scoring 27 goals, including one in the 2014 FA Cup final success over Hull City.
Wenger told the club website: “We’re delighted to have extended the contracts of Santi and Theo. Both are top quality players who are hugely important and influential to our squad.
“As well as their huge contributions on the pitch, they both have a great deal of experience and are very popular off the pitch.
“We’re very pleased with them both signing contract extensions, as it provides our squad with further stability of quality.”