The appeal was received by the Supreme Court in Stockholm on Tuesday, court spokeswoman Tove Levelind said.
Earlier this month, , upholding a district court decision to detain him for questioning.
Assange, whose whereabouts are unknown, is wanted by Sweden internationally concerning allegations against him that include rape and sexual molestation. They stem from his encounters with two Swedish women during a visit to the Nordic country in August.
He has denied the allegations, calling them part of a smear campaign.
He has not been formally charged.
, including diplomatic cables and sensitive U.S. State Department documents.
The 39-year-old Australian has angered the U.S. and other governments with such disclosures, including secret documents about the wars in Afghanistan and Iraq.
During his August visit to Sweden, Assange applied for a residency permit in the country, where the WikiLeaks site has some of its servers and laws offer strong protection for whistle-blowers. Sweden rejected the request.
On Monday, Ecuador's deputy foreign minister, Kintto Lucas, praised Assange for his work and offered him residency in the leftist-run Andean nation "without any kind of trouble and without any kind of conditions."
More on the Wikileaks Diplomatic Cables:
Leaked Docs: Karzai Freed Connected Drug Dealers
Wikileaks: China's Influence In N. Korea Limited
Post-9/11 Intel Sharing at Risk after WikiLeaks
Leaked Memos Envision North Korea Collapse
Keeping Secrets, Even From WikiLeaks
U.S. Opens WikiLeaks Criminal Investigation
Links to Leaked Cables:
"State Secrets" Section (New York Times)
The US Embassy Cable (Guardian)
Die Botschaftsdepeschen (The Message Dispatches) (Der Spiegel, in German)
Los papeles del Departamento de Estado (El Pais)
Wikileaks: Dans les coulisses de la diplomatie americaine (Le Monde)