Amanda Ammar also put her name into the mix for Sochi after winning the women's skiathlon.
Skiathlon is a form of cross-country skiing that combines the classic and skating styles of skiing.
"This is so huge. You just dream of this day. It feels amazing," said Killick. "I never really thought I had it until that final hill. So many people have helped me a long the way and it is just awesome to share it with them."
The 24-year-old Killick, from Fort McMurray, Alta., skied in the pack until the final lap of the 15-kilometre classic-portion of the race where he began to make his move and never looked back. He entered the transition into the 15-kilometre skate leg first and continued to open his lead on the field.
He cruised home to victory, winning the 30-kilometre skiathlon race with a time of one hour, 26 minutes 53.9 seconds to all but officially secure his spot in Sochi, Russia this February.
Cross Country Canada will select just one men's distance skier for the Olympics.
Killick was favoured to win Thursday's 15-kilometre classic-ski race, but was reeled in on the final lap by 10-time Paralympic medallist Brian McKeever of Calgary. McKeever's Olympic hopes came to a halt on Sunday when he was not able to respond to Killick's break on the pack, and finished eighth.
"I did think about the other day and was a little worried because I blew up on that final lap Thursday," said Killick. "I think that race just reinforced to me how important every second and every corner is out there. That is what I thought about today."
McKeever was impressed with his teammate's finish in the skiathlon.
"That was an impressive performance," said McKeever. "Graeme skied awesome and I'm very happy for him. He showed great form, and that is what you want for the Olympics."
Jesse Cockney, who has also split time on the World Cup and domestic race circuit with Killick, put in a hard effort to finish second at 1:27:52.4. Cockney, from Canmore, Alta., put his name in the running for Sochi after winning Saturday's sprint race. Michael Somppi of Thunder Bay, Ont., was third at 1:27:52.7.
Meanwhile, Ammar of Onoway, Alta., gutted out a strong performance in the women's 15-kilometre skiathlon race. The 27-year-old led wire-to-wire through the 7.5-kilometre classic-ski course, followed by 7.5 kilometres of skate-skiing to post a winning time of 49:16.9.
The victory puts Ammar in contention for the final women's distance athlete that Cross Country Canada will nominate to its Olympic team on Tuesday. Athletes need to win one of the selection races to be considered for nomination.
Whitehorse's Emily Nishikawa won the women's 10-kilometre classic-ski race on Thursday.
Brittany Webster of Caledon, Ont., skied to the silver for the second-straight race. Webster stopped the clock at 49:22.3. Quebec's Anne-Marie Comeau was third at 49:47.1.