Tiglao, a former journalist, said he would fly to Japan next week to become a visiting professor at Kyoto Universitys Center for Southeast Asian Studies.
Tiglao said his time with President Arroyo had been exciting, but the fellowship would be "an opportunity for me to refresh my intellectual, spiritual and even physical resources."
Tiglao, 49, became Mrs. Arroyos official spokesman 12 months ago, shortly after her deposed predecessor, Joseph Estrada, was detained to go on trial for a string of corruption charges.
Presidential Management Staff chief Silvestre Afable will take Tiglaos post for the next six months.
Tiglao has yet to take his oath of office as the new Press Secretary vice Noel Cabrera who resigned last month, and was offered the chairmanship of a government-controlled financing institution.
Afable, 51, is no stranger to the Office of the Press Secretary (OPS) since he also served as officer-in-charge of the Philippine Information Agency which operates under the OPS.
Tiglao made the surprise announcement during his regular press briefing at the Palace in the presence of Afable and his two deputies, Press Undersecretaries Roberto Capco and Manuel Sanchez.
Tiglaos third deputy at the OPS, Carmen Suva, went on terminal leave after availing herself of optional retirement.
"I will try to do my best to fulfill it (fellowship) in three months and get back to work," Tiglao said.
A Palace source said Tiglao would be "paid very handsomely" for his job in Kyoto.
"I heard the amount was really something he could not refuse because his university post is heavily funded," the source said. Marichu Villanueva