The market had also started to get a "little complacent" ahead of an announcement from the Federal Reserve following the conclusion of a two-day policy meeting on Wednesday, said Scotia Capital currency strategist Shaun Osborne.
"With the Fed on the horizon it seemed prudent of the markets to cover some of the dollar shorts," he said.
The Fed began its meeting Tuesday with no change to interest rates expected. However, investors will be looking for the U.S. central bank's outlook on trimming its $4.5 trillion in bond holdings, said Eric Nelson, currency strategist at Wells Fargo.
The dollar index had fallen to its lowest since June 2016, to 93.638. It has fallen nearly 4 percent over the last month and more than 8 percent this year. It was last up 0.11 percent at 94.08.
The euro had risen more than half a percent to $1.1711, matching its high from Aug. 24, 2015, and just below its highest since January 2015. That represented an important technical level, Nelson said.
The euro was last up 0.09 percent at $1.1648. The dollar rose 0.76 percent against the Japanese yen to 111.93 yen.