The 24-year-old is the latest to confirm his participation in the January tournament, after former champions David Ferrer and John Isner were announced last week.
Sock has a good record in Auckland so he was an inevitable target. He reached the quarterfinal on his first visit in 2014 - beating Tommy Haas on the way - and had one of the best tournaments of his career last January.
He upset third seed Kevin Anderson in the last eight, then beat Ferrer in one of the best matches of the week, coming back from a set down to win a gripping semifinal 3-6 6-1 6-2.
Sock didn't see out the final against Roberto Bautista Agut - he retired in the second set after the effects of a virus became too much - but that didn't take too much gloss off his week.
"I always love coming back [to Auckland]," said Sock. "It's a really cool city. It's kind of a laid back event. For me it's the best lead up to the first Grand Slam of the year."
Sock has long been earmarked as a new hope for American tennis, ever since his Junior US Open triumph in 2010. He has achieved plenty of success in doubles, including a Wimbledon triumph and seven Masters finals (two wins) but over the last 18 months has begun to convert on his promise in the singles arena.
Sock won his first singles title in Houston last April, and has reached three other finals since (Stockholm, Auckland and Houston again). Sock, who is currently ranked No 23 in the world, has already beaten three top 10 players this year.
"Jack is playing at a high level and is really starting to fulfil the potential we saw in him a number of years ago," said tournament director Karl Budge. "He has a really big game. Stats say his forehand is bigger than [Rafa] Nadal's and matched with serving at more than 220km/h, he will be a handful."
More player signings will be announced in the coming weeks with the full men's and women's line-up to be announced late November.
The ASB Classic will span for two weeks; the women's tournament runs from January 2nd to 7th followed by the men's tournament from January 9-14.
