At a conference in Jackson Hole, Wyoming, Yellen said that reforms put in place after the 2007-2009 financial crisis have strengthened the financial system without impeding economic growth, and any future changes should remain modest.
"We're seeing a little bit of a relief that (Yellen) wasn't hawkish rally in Treasuries, but it's minor," said John Briggs, head of strategy for the Americas at NatWest Markets in Stamford, Connecticut.
Benchmark 10-year notes gained 5/32 in price to yield 2.176 percent, down from 2.194 percent on Thursday.
European Central Bank President Mario Draghi was also due to address the annual economic policy conference later on Friday.
Investors will watch for any signals that the ECB is close to paring its bond purchases, though two sources have told Reuters that Draghi will also not deliver any new policy message at the event.
Yields for benchmark bonds have held in a tight range since falling to almost two-month lows last Friday on concerns about political discord in Washington and tensions between the United States and North Korea.
Data this Friday showed that new orders for key US-made capital goods rose slightly more than expected in July and shipments surged, suggesting an acceleration in business spending early in the third quarter.