Customs officials apparently questioned the 20-year-old for two hours inside the airport's Tom Bradley International Terminal at 4pm.
Justin Bieber's entourage was standing around waiting for him, reported E!Online.
Around 6.20pm, the Canadian singer was finally released and allowed to leave.
"It was a routine secondary set of questioning that Justin has to go through now every time he comes back in the country because he's a foreign national," a source said.
Justin Bieber later took to Twitter to assure his fans he is doing well after the hold-up, writing, "Life is good. Keep it positive always."
The 'Baby' hitmaker was also briefly detained while traveling from Canada to New Jersey for Super Bowl festivities in February.