The 34-year-old devout Muslim had expressed his desire to retire after the World Cup.
But he has since changed his mind following Pakistan's disastrous performances in South Africa.
"I have consulted my family, friends and religious scholars and on their advice have decided to continue my international cricket. I have conveyed my decision to the cricket board," said Anwar in a statement.
Anwar was among the few Pakistan players who gained any credibility from the World Cup debacle.
He was suffering a drastic loss of form until he scored a superb century in Pakistan's six-wicket defeat to arch-rivals India at Centurion.
His availability will boost the Pakistan Cricket Board (PCB), which is seeking a new national coach following Richard Pybus' resignation.
Anwar is now expected to be part of Pakistan's squad for their triangular one-day series against Sri Lanka and South Africa in Sharjah on 1 April.