The striker will have surgery on Friday after injuring an ankle during the club's pre-season tour of New Zealand
The former Liverpool man injured an ankle during the club's pre-season tour of New Zealand with the club originally stating he would miss both of their tour games.
"Andy Carroll will miss both games on the Football United tour of New Zealand as a precautionary measure after developing a sore left ankle during training," read a statement on the club's website.
"After assessment by the club's medical experts, it was decided to let the England international rest for both remaining games and receive intensive treatment to ensure he is fit for the start of the season."
However, Carroll has now confirmed via Twitter that he is set to undergo surgery on the problem and will miss the start of the Hammers' season.
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.