According to Swiss daily Blick, the 170 infantry soldiers from the neutral country wandered more than a mile across an unmarked border into the tiny principality early Thursday before realizing their mistake and turning back.
A spokesman for the Swiss army confirmed the story, but said that there were unlikely to be any serious repercussions for the mistaken invasion.
"We've spoken to the authorities in Liechtenstein and it's not a problem," Daniel Reist told The Associated Press on Friday.
Officials in Liechtenstein also played down the incident.
Interior Ministry spokesman Markus Amman said nobody in Liechtenstein had even noticed the soldiers, who were carrying assault rifles but no ammunition. "It's not like they stormed over here with attack helicopters or something," he said.
Liechtenstein, which has about 34,000 inhabitants and is slightly smaller than Washington, D.C., does not have an army.