The Welsh openside had to keep the appointment quiet until the official selection press conference in London but he admits he wasn't quite so able to hide his initial reaction immediately after putting the phone down on the Lions' boss.
"It was just absolute joy - I couldn't believe it," Warburton told the BBC.
"I was absolutely delighted. I ran down the stairs to tell my fiancé as if it was Christmas morning for a small boy!
"I had a huge smile on my face, and I've still got it now.
"It's just surreal. I've always wanted to make a Lions touring squad - that's been a target since I was a young boy - but I never even dreamt of being captain. Having that honour is unbelievable."
Warburton follows a whole host of legendary Lions in holding the ultimate responsibility, with the likes of Paul O'Connell, Brian O'Driscoll, Martin Johnson and Willie John McBride all having led Britain and Ireland's elite before the 24-year-old.
Just thinking about those famous names leaves the affable openside somewhat wide eyed and he insists his selection doesn't mean he sees himself in a similar light.
"No chance, no way at all! That's what seems so strange and surreal to be honest," added Warburton.
"Those guys are all legends in my eyes. They've done a heck of a lot for the game and are all amazing rugby ambassadors. That's why it probably won't sink in for a long time.
"To play for the Lions is what it's all about. When you think about playing rugby from a really young age, you want to play for your local club and I've been lucky enough to with the Blues. Then you want to play for your country, which is incredible.
"But when you put all four teams together and consider the standard of all four nations, to be part of the crème de la crème in Britain and Ireland is surreal."