Henry suffered a tear during Ireland's 40-9 win over Samoa on Saturday afternoon and will miss the remainder of his country's autumn Tests against Australia and New Zealand.
More importantly for Ulster, Henry faces a race against time to be fit for their European double header with Benetton Treviso, starting with the home fixture at Ravenhill on the evening of Saturday, December 7.
"It's really disappointing for Chris to be literally hamstrung. He tried to play through it, but it was determined that it wasn't something he could play on with," said Ireland head coach Joe Schmidt.
"Unfortunately Chris Henry suffered a hamstring tear on Saturday," added Ireland team manager Mick Kearney. "So he will miss the rest of the Guinness Series and Shane Jennings has been called in as a replacement."
Henry has been a key figure for Ulster in recent seasons, having started all but one of their Heineken Cup games over the past two campaigns. The 29-year-old was an ever present in Europe last term and started eight of his province's nine matches on the way to the Heineken Cup Final in 2011/12.
He has again started both fixtures in this season's competition, helping Ulster to back-to-back wins against Leicester Tigers and Montpellier as they surged to the top of Pool 5.
Fellow Ulster star Tommy Bowe was also injured in Ireland action at the Aviva Stadium but his calf injury isn't seen as serious even though Leinster's Luke Fitzgerald has been called up as cover for the national side.
"Tommy Bowe got a kick on his calf early in the game and was removed as a precaution. It's sore and bruised, although he is likely to recover and Luke Fitzgerald has just been called in as a replacement," said Schmidt.