Najib al-Udaini, 30, who was seized by armed men on January 29, was turned over late on Sunday, said Filipina congresswoman Faisah Dumarpa, who negotiated with the abductors for his release.
The unnamed abductors had earlier demanded up to one million dollars for his freedom but Dumarpa said no ransom was paid. She said he was released after negotiations, without giving details.
Udaini, looking tired and sleep deprived, was presented to reporters in a hotel in the south. He thanked the negotiating team and the Philippine government in Arabic, but did not discuss his ordeal.
The southern Philippines has been plagued for years by armed bands, including Islamic militants, who engage in kidnapping for ransom, often targeting Christians and foreigners.
Some kidnap victims have been beheaded after failures to pay ransoms.
Regional police commander Senior Superintendent Panare Adap said Udaini's kidnappers were "a small time group" that was only after a ransom and did not have a political agenda.
Udaini had been in the south of the country, helping with aid projects for the World Assembly of Muslim Youth, an Islamic group whose website says that it engages in educational and religious projects.
Regional police official Senior Superintendent Salik Macapantar praised Udaini's work in the south, saying he had built mosques and schools in Muslim communities.
"He's a good man and active in humanitarian projects," Macapantar said.