Willingham, who is also under contract for $7 million next year, now can't be traded to any club this season.
"I'm just glad it's over," Willingham said. "Now I know where I'm going to be."
Willingham said he knew a trade wasn't completed when he didn't hear anything from the Twins or his agent on Friday, but he was never officially notified by anyone he wasn't traded.
But he was happy to be in the Twins' lineup on Friday against the Rangers, and said he prefers staying with the club.
"I'm comfortable here, so I'd like to stay here," Willingham said. "The bottom line is I didn't have any control, so I didn't worry myself with it."
Rhett Bollinger is a reporter for MLB.com. Read his blog, Bollinger Beat, and follow him on Twitter @RhettBollinger. This story was not subject to the approval of Major League Baseball or its clubs.