The former "Baywatch" and "Knight Rider" star has been promoting Cumberland Farms iced coffee since last year, and the signs have become popular items to steal, police say.
Hasselhoff tweeted about Tuesday's robbery in Shelton, urging people to pray that the 36-year-old clerk makes a full recovery.
"I am shocked & truly saddened about the Cumberland farms store clerk tragedy," Hasselhoff said in a posting on his official Twitter account. "My heartfelt thoughts and prayers are with him and his family!"
The Cumberland Farms worker, whom authorities have not named, suffered a head injury when he was hit by the thieves' SUV and dragged, police said. He remained hospitalized in critical condition Wednesday.
The clerk saw a man cut two of the Hasselhoff signs off a light pole and put them in the SUV, authorities said. The employee was injured trying to confront the suspects as they sped away.
A 19-year-old man came forward Tuesday evening and confessed that he was the driver of the SUV, Shelton police said Wednesday. Authorities have not released the man's name, but say he is cooperating. Police say two other people were involved in the theft.
Lt. Robert Kozlowsky said police have recovered the two stolen signs.
Cumberland Farms sent several employees to Connecticut to offer any help they can to the clerk and his family, company spokeswoman Carin Warner said.
Warner said the number of thefts of the Hasselhoff signs has significantly decreased since last year.
Cumberland Farms, based in Framingham, Mass., has nearly 600 stores in 11 states and employs more than 6,000 people.