The former Liverpool man picked up the problem during the club's pre-season tour of New Zealand with the club originally stating he would miss both of their tour games.
However, West Ham chairman David Gold has subsequently confirmed the severity of the striker's injury with the 25-year-old set for a long spell on the sidelines.
"I'm sorry to inform you that AC has torn ankle ligaments and will have an operation tomorrow," he wrote on Twitter. "Andy will be back in about 4 months."
Carroll also took to Twitter to reveal his disappointment as he prepares to undergo surgery to correct the problem on Friday.
Carroll joined West Ham from Liverpool last summer after impressing for the Hammers during a loan spell from the Reds.
Going under the knife tomorrow morning and absolutely devastated to be missing the start of the season!! pic.twitter.com/kTAYuF0YGB— Andy Carroll (@AndyTCarroll) July 24, 2014
However, the striker struggled with injury throughout last season and managed just 16 games for Sam Allardyce's side as the Hammers finished the campaign in 13th place.
West Ham kick off the new Premier League campaign at home to Tottenham on August 16.