The U.S. dollar was on track for its biggest weekly percentage decline against the yen since the 2008 financial crisis in the aftermath of the Bank of Japan's decision not to ease policy further, while strong euro zone growth data boosted the euro.
The dollar was last down 1.3 percent against the yen at 106.72 yen on Friday, near an 18-month low. The dollar was last down about 4.5 percent against the yen for the week, putting it on track for its biggest weekly loss since October 2008.
The dollar also tumbled against the euro, with the euro hitting its highest against the dollar in two and a half weeks. The euro was last up 0.8 percent against the dollar at $1.1448.
The dollar index, which measures the greenback against a basket of six other major currencies, hit an eight-month low and was last down 0.7 percent at 93.12.