U.S. prosecutors have indicted Assange on 17 espionage charges and one charge of computer misuse over WikiLeaks’ publication of thousands of leaked military and diplomatic documents a decade ago.
In January, a lower court judge refused an American request to send Assange to the US to face spying charges over WikiLeaks' publication of secret military documents.
Swedish prosecutors on Friday dropped their investigation, but Assange still faces the risk of arrest in Britain.
The woman who has accused WikiLeaks founder Julian Assange of rape has slammed the decision by Swedish prosecutors to drop an investigation as a "scandal".
Assange took refuge in Ecuador's embassy in London in 2012 to escape extradition to Sweden to answer questions about sex-crime allegations from two women.