Bush, 91, who served as America’s 41st president, was last hospitalised in Houston, Texas, for a week in December 2014 after experiencing breathing difficulties.
“‘41’ fell at home in Maine today and broke a bone in his neck,” spokesman Jim McGrath said on Twitter following the accident, using his presidential nickname.
“His condition is stable — he is fine — but he’ll be in a neck brace.”
Bush was taken to Maine Medical Centre in Portland.
Matt Paul, a hospital spokesman, said Bush was transported to hospital Wednesday afternoon.
“He was diagnosed with a fracture in his neck,” said Paul. “He is in stable condition and will be wearing a neck brace.”
Paul said the former president would remain in the hospital overnight, adding it was “too early to say when he will be released”. McGrath said Bush will stay in the hospital “as long as needed.”
Bush is the father of former president George W. Bush and of former Florida governor Jeb Bush, who is now seeking the Republican nomination for the 2016 presidential election.
The elder Bush, a Republican like his sons, served as vice president for eight years during Ronald Reagan’s two terms in the White House before being elected president, defeating former Massachusetts governor Michael Dukakis, the Democratic nominee, in 1988.
Bush took office in 1989 and served four years in the White House, during which he organised the US-led military coalition that defeated Iraqi forces after Saddam Hussein invaded Kuwait.
He lost his 1992 re-election bid to Democrat Bill Clinton.
Bush previously served as a congressman, a UN ambassador, a US envoy to China, and director of the Central Intelligence Agency before becoming Reagan’s running mate in 1980.
A Navy pilot during the Second World War, he celebrated his 90th birthday on June 12, 2014, by skydiving near Kennebunkport, Maine, with the Army’s Golden Knight parachute team. He currently suffers from Parkinson’s disease and cannot use his legs.