The victim, in his 30s, was attacked by a group of five or six youths in Grosvenor Street, Cheltenham, on Friday.
He was known to his attackers, Gloucestershire Police said.
All three boys were arrested on suspicion of causing grievous bodily harm (GBH).
The eldest, aged 14, was arrested separately from the younger pair.
Police appealed for witnesses to the attack, which happened at about 17:30 BST.

The suspect, 26 and of no fixed address, was detained by West Midlands Counter Terrorism Unit officers after arriving on a flight from Turkey.
He is being held in custody in the West Midlands.
West Midlands Police said the arrest was pre-planned and there was no threat to the safety of the flight or the airport.

Science and research should be a priority in the talks between the UK and the EU, says the Russell Group of research intensive universities.
Any barriers "would be bad for the UK and bad for Europe", said the group's acting director, Tim Bradshaw.
His comments come as the EU prepares to authorise the start of the talks.
The EU's chief negotiator, Michel Barnier, is due later on Monday to seek a formal mandate from the European Council in Brussels to begin negotiations.
Mr Barnier expects the talks to begin immediately after June's general election.
The Russell Group says there will be "no winners" if Brexit results in barriers between researchers and has pledged to work with "all sides to secure a positive outcome".
Dr Bradshaw said there had been "huge breakthroughs in medicine, engineering, and any number of fields" as a result of joint working, which he promised would continue after Brexit.
"We want to maintain the closest possible relationships with colleagues across the EU, and research must be a priority during talks," he added.
He called for the rights of EU students and staff at UK universities to be guaranteed after Brexit.
"We value our EU colleagues very highly and need urgent assurances, that after Brexit, they will retain the same rights to stay and work in the UK that they have now.
"Nearly half of all UK academic articles result from international collaboration and EU member states are some of our biggest partners.
"These relationships improve the quality of UK research and underpin the strength of our science base."
UK universities are among the biggest beneficiaries of the EU's huge Horizon 2020 research fund.
Non-EU countries can also draw on the fund if they contribute to it - but a major condition of countries being able to participate is allowing freedom of movement for researchers, a potential stumbling block in the talks.
The Conservative party manifesto, promises to "collaborate in science and innovation" with EU member states.
The manifesto also pledges to secure the entitlements of EU nationals in Britain and British nationals in the EU.
"There may be specific European programmes in which we might want to participate and if so, it will be reasonable that we make a contribution," the document adds.
Labour's manifesto promises that the party in government would "ensure that the UK maintains our leading research role by seeking to stay part of Horizon 2020 and its successor programmes and by welcoming research staff to the UK".
The party also says it will seek to maintain membership, or equivalent, with European organisations that offer benefits to the UK such as Euratom and the European Medicines Agency.
The Liberal Democrat manifesto warns that "the Leave vote has already started to affect existing and proposed research programmes".
"We will campaign against any reduction in investment in UK universities and for their right to apply for EU funds on equal terms."
Manifestos have not yet been published for the SNP, UKIP or the Green Party.
A teenager and two 12-year-old boys have been arrested after a man was stabbed and hit with a baseball bat in a street attack.
[NEXT_CONCEPT]
A man has been arrested at Heathrow Airport on suspicion of Syria-related terror offences, police have said.
[NEXT_CONCEPT]
Barriers to research collaboration in Europe as a result of Brexit would harm scientific progress, says a group of leading UK universities.