In Tokyo afternoon trade, the greenback bought 79.41 yen, slipping from 79.74 yen in New York on Wednesday, while the euro weakened further to 97.16 yen from 97.58 yen in US trade.
The euro was little changed at $1.2235, from $1.2238 in New York.
After a two-day policy meeting, the Bank of Japan left rates unchanged and tweaked its 70 trillion yen ($880 billion) asset-purchase programme but kept the size of its main policy tool steady.
The bank's decision to buy five trillion yen more in treasury discount bills while cutting its fixed-rate loans by the same amount was likely to have little effect, analysts said.
Major policy moves would have been expected to spark yen selling.
"In practical terms, it's an easing," said Tsunemasa Tsukada, chief manager of forex and financial products trading at Mitsubishi UFJ Trust and Banking.
"Still, the size of the asset purchase programme hasn't increased in net terms. So the effects of easing should be limited. It's somewhere between unchanged and an easing."
Meanwhile, the euro remained weak but clawed back after hitting a two-year low of $1.2210 on Wednesday, shortly after minutes from a US Federal Reserve meeting suggested the central bank was split on further stimulus.
Several policymakers at the Fed urged the central bank to look at new tools to bolster the financial system amid a weak recovery, but the minutes also showed the Fed was split on how, when and if to provide more stimulus.
Cautious optimism about an austerity package for Spain was largely offset by worries that Italy may have to tap a eurozone rescue fund, dealers said.
The dollar mostly firmed against other Asia-Pacific currencies.
It bought Sg$1.2672 from Sg$1.2665 on Wednesday, 55.57 Indian rupees from 55.40 rupees, and 41.92 Philippine pesos from 41.89 pesos.
It also rose to 31.77 Thai baht from 31.73 baht, to Tw$29.97 from Tw$29.94, and to 1,148.20 South Korean won from 1,143.75 won.
The dollar was flat at 9,463.00 Indonesian rupiah.
The Australian dollar bought US$1.0180 from US$1.0203, while the Chinese yuan changed hands at 12.48 yen against 12.43 yen.