Cowan announced yesterday he had re-signed with New Zealand and Southland rugby through to the end of the 2012 season.
The Highlanders captain wanted to secure his future as soon as possible and was able to come to terms with the New Zealand Rugby Union.
"It was a pretty easy decision, in the end.
"I love this country and it's time for me to give something back to a sport that has done so much for me," Cowan said.
Cowan, who turns 28 next month, has established himself as the No 1 All Black halfback, fighting off other contenders with his competitiveness and outstanding defence.
He now has 32 caps and will, barring injury, almost certainly play in the World Cup when New Zealand hosts the tournament next year, for the first time since 1987.
"Obviously the World Cup is in mind and that was a big reason to stay.
"I've got goals that I want to reach and hopefully, I can get there.
"I still don't feel I'm an established All Black yet.
"I think I've done well when I've been there but believe I've got plenty to offer."
Cowan said he never seriously considered taking up an offer to play overseas.
His decision is good for the All Blacks but it is especially welcome for the Highlanders - Cowan is in his second year as captain and is the most experienced player, with 68 caps, in the squad - and Southland.
Chief executive Roger Clark said Rugby Southland was delighted to hold on to Mataura product Cowan, who has made 92 appearances for the Ranfurly Shield-holding Stags.
"Jimmy's presence in the Southland set-up has been instrumental in local players committing to the province and in no small way has played a part in the consistently good performances of the Stags over the past five years," he said.
Cowan will have a new face beside him when the Highlanders play the Blues at Carisbrook tomorrow night, with Michael Hobbs earning his first start for the team.
Hobbs replaces the injured Matthew Berquist (hamstring) but possibly would have started anyway, given his performance off the bench against the Crusaders.
In the only other change to the starting XV, Steven Setephano is at No 8, in place of Nasi Manu, who is out of rugby for at least a month with a knee injury.
Southland wunderkind Robbie Robinson gets his first chance in the reserves, while All Black lock Tom Donnelly will earn a 50th cap, as the Highlanders seek to regain the Gordon Hunter Memorial Trophy.
The Blues have selected former Highlanders fullback Paul Williams, with Rudi Wulf moving to the wing and Rene Ranger dropping to the bench.
Highlanders v Blues
Carisbrook, tomorrow
Highlanders: Israel Dagg, Ben Smith, Jason Shoemark, Jayden Hayward, James Paterson, Michael Hobbs, Jimmy Cowan (captain), Steven Setephano, Alando Soakai, Adam Thomson, Tom Donnelly, Josh Bekhuis, Clint Newland, Jason Rutledge, Jamie Mackintosh.
Reserves: Jason Macdonald, Chris King, Hayden Triggs, John Hardie, Sean Romans, Robbie Robinson, Fetu'u Vainikolo.
Blues: Paul Williams, Rudi Wulf, Rene Ranger, Isaia Toeava, Benson Stanley, Joe Rokocoko, Stephen Brett, Alby Mathewson, Viliami Ma'afu, Serge Lilo, Jerome Kaino, Anthony Boric, Kurtis Haiu, John Afoa, Keven Mealamu (captain), Tony Woodcock.
Reserves: Tom McCartney, Charlie Faumuina, Filo Paulo, Peter Saili, Chris Smylie, Daniel Kirkpatrick, Rene Ranger.
