The yield on the benchmark 10-year Treasury notes, which moves inversely to price, was higher at around 2.237 percent, and the yield on the 30-year Treasury bond was higher at 2.779 percent.
The Federal Reserve may have overstated the strength of the labor market and the rate of inflation, leading to monetary policy ahead that will be easier than previously thought, Yellen said Tuesday. The market was barely changed after Yellen's speech.
"She seems to be a lot more cautious than" after the FOMC meeting, said Ian Lyngen, head of U.S. rate strategy at BMO. Lyngen had seen a turn in the equity market while awaiting Yellen's speech.
"The market has now priced in a December move," Lyngen added.
In an auction of Treasurys which closed Tuesday afternoon, $26 billion in two-year notes auctioned at 1.462 percent, with 45.6 percent at high yield and a bid-to-cover of 2.88.