"We can't begin tonight's show without acknowledging the passing of a television pioneer and my dear friend Dick Clark," Seacrest said.
"Without Dick, a show like this would not exist. He will be missed greatly. Our thoughts and our prayers go out to his family."
Seacrest, who joined Clark as co-host of ABC's New Year's Eve telecast Dick Clark's New Year's Rockin' Eve in 2005, added: "I know that he's in a better place, saying, 'Hey, let's get on with the show'. You got it, boss."
The broadcaster and E! News host described Clark as "one of the greatest influences" on his life in a Twitter post earlier today.
Watch part of Dick Clark's appearance on TV documentary 'This Is Your Life' in 1959 below: