"I try not to make or set opinions about people I haven't had any substantive interaction with," Michelle Obama said in an interview scheduled to air on CNN's Larry King Live. "I mean, I know what you see on TV."
Asked later if she considered the 2008 vice presidential nominee to be a "phenomenon," the first lady again withheld criticizing Palin.
"Again, I mean, I think it's wonderful to have strong, female voices out there, but I don't know her," Obama said.
With her keynote address at last week's Tea Party convention, Palin has continued a pattern of hard-hitting critiques of President Obama that began on the campaign trail in 2008.
The first lady did defend her husband's record after a year in the Oval Office. "Democracy is about critique and the president is not immune to criticism," she said.
"I think he is doing a phenomenal job," she continued. "We have to think about where he was when he took office. We were on the brink of a depression - worse than anyone really ever imagined. And I don't think the country really knew how bad things were.
And because of some important steps; quick thinking; smart, strategic thinking, we're not even talking about that. We've got to do more on jobs. We need to get health care [reform] done. There's a lot of work to be done. We need to do more to improve the civility in Washington and if there's a disappointment - Barack wishes that we'd come farther in that effort."
The first lady appeared on CNN the same day she announced an initiative Tuesday to fight childhood obesity.
Note: The Michelle Obama interview airs on Larry King Live Tuesday beginning at 9 p.m. ET.