Police foiled another attack when they arrested a would-be suicide bomber at former president Habib Bourguiba's tomb in the seaside town of Monastir.
No group has claimed responsibility for yesterday's attacks, but the Islamist-led government has been combating Ansar al Sharia militants it says are tied to al Qaeda's North Africa affiliate.
Interior Ministry spokesman Mohammed Ali Aroui said: "The two suicide bombers are radical Islamist jihadists. They are Tunisians but had been in a neighbouring country."
The first bomber had initially tried to enter the Riadh Palms Hotel with a suitcase but when he was not allowed in, he ran onto the beach and blew himself up. No-one else was hurt.
The bombing is bad news for the tourism industry in Tunisia, which attracted 5.8 million mostly European visitors to its Mediterranean beaches and desert tours in 2012. Tourism is still recovering from the 2011 uprising that toppled the North African country's autocratic leader Zine al Abidine Ben Ali.
Tunisia's stock market dropped 0.95% after the bombing.
Mohamed ali Toumi, head of Tunisia's federation of travel agencies, said: "We don't know what the consequences will be right now, but in 24 hours we will find out. Whatever happens it will be negative because this is the first time they have attacked a hotel."
Al Qaeda carried out Tunisia's only previous suicide bombing in 2002 when 21 people were killed at a synagogue on the island of Djerba.
Since the 2011 uprising, Islamists have pressed for strict Sharia law to be imposed in one of the Muslim world's most secular countries, which has strong ties to Europe.
Oppressed and jailed under Ben Ali, conservative Salafists - followers of a puritanical strain of Sunni Islam - have had more freedom to express their fundamentalist views since 2011.
But violent, hardline Islamists have also attacked alcohol sellers, art shows and theatre plays they say are against Islam, and have taken over mosques.
The rise to power of an elected Islamist-led government has fuelled fears of many secular Tunisians that women's rights and liberal educational traditions may be eroded.
The ruling Ennahda party says even ultra-orthodox Islamist views must be accommodated in Tunisia's fledgling democracy, but that there is no place for armed militants.
Authorities say the militants have acquired weapons and training in neighbouring Libya, where the central government has failed to impose order since the 2011 fall of Muammar Gaddafi.
Ennahda accused Ansar al-Sharia militants of being behind the assassination of two secular opposition leaders this year.
Those attacks set off months of protests from opposition supporters who said Ennahda had been too lenient on hardline Islamists. Ennahda has agreed to step down within the next three weeks to end the unrest and allow a caretaker government to govern until elections.
Ansar al Sharia was also blamed for inciting an attack on the US embassy a year ago, when Islamist protesters stormed the building. The group's leader is a former al Qaeda veteran who once fought in Afghanistan.