Claiming the 'AN Other' spot in the 25-man squad named by Declan Kidney, Whitten got a telephone call last Monday to confirm his tour place, with his Ulster team-mate Paddy Wallace ruled out of the tour on medical advice.
The Ulster Academy member, who has played eight times for the province's senior team this season, is aiming to make the most of this unexpected opportunity in the Ireland set-up.
"It was great to have made the jump from the Academy to the seniors this season. At the beginning of the season, I would never have dreamt of being selected for so many games," he admitted.
"Now to receive a call-up for an Irish tour, it's a dream come true. The whole experience is so unexpected.
"I am just thrilled to be playing rugby at such a high standard, and to be given the chance to play at touring level with players such as Rory Best, Peter Stringer and Denis Leamy."
Whitten, a former underage international and captain of Queen's University, is a powerfully-built centre who has dovetailed well with fellow tourist Darren Cave in Ulster's midfield.
The playing squad, Declan Kidney and his coaching staff and team officials flew from Dublin to Vancouver via Heathrow on Sunday, ahead of next Saturday's tour opener against Canada at the Thunderbird Stadium (2pm local time/10pm Irish time).
The players had their first training session on Monday at a local school, with Tuesday's team announcement for the Canada game scheduled for 1.30pm local time/9.30pm Irish time.
Unfortunately, Whitten's Ballymena and Ulster colleague Chris Henry has emerged as a serious doubt for the tour.
One of 13 uncapped players named in Kidney's touring party, back rower Henry suffered a recurrence of a shoulder injury in Ulster's Magners League loss to the Scarlets over the weekend.
The 24-year-old, a former captain of the Ulster and Ireland Schools sides, has enjoyed a whirlwind campaign in Matt Williams' Ulster squad.
He made his senior debut for the province against Harlequins in January and has since racked up ten caps.
Commenting on the injury, Ulster boss Williams said: "Chris is in real pain after hurting the AC joint in his shoulder. He picked up the injury initially against Harlequins and has taken another bang on it.
"He is a doubt for the tour which is disappointing.
"It would have been great for Chris to get some caps under his belt because he would have learnt so much about the intensity and mental aspects of playing at that level.
"Chris will still go and meet up with the squad and we'll let the medical team make the final decision."