He also attacked the debate’s moderator Lester Holt who he said was biased towards Clinton.
His comments follow an underwhelming performance in the debate, with scientific polls, focus groups and the markets handing the win to Clinton.
In the aftermath, Trump insisted every poll showed him as the winner, citing many online polls handing him the victory, but also complained about his microphone and told supporters in a subsequent appearance he had been “holding back” in the debate, because he didn’t want “to embarrass” Clinton.
But he has now offered a new conspiracy theory to explain why many said Clinton won the debate.
Speaking at a rally in Waukesha, Wisconsin, on Wednesday, Trump said he believed Google was rigging search results against him, The Independent reported.
He said: “Google search engine was suppressing the bad news about Hillary Clinton.”
“How about that? How about that?” he said to a cheering crowd.
The Independent has contacted Google for comment on the accusations.
Trump's claims followed remarks he made to Fox News, in which he said that during the debate, Holt gave him harder questions than he gave to Clinton.
Trump had originally been complimentary about Holt’s performance. “I said good things right after the show, but after reviewing it and after seeing the way he badgered, and even the questions I got… I was disappointed,” he said.
“[He] was much, much tougher on me than he was on Hillary,” he added.
“Anyone who complains about the microphone is not having a good night”, Clinton told reporters after the debate.
In an appearance at a rally in New Hampshire, she said the US is in the midst of “one of the strangest elections” she had ever seen.
A new poll by Reuters/Ipsos released on Wednesday evening found that 56 percent of American adults felt that Clinton did a better job than Trump at their first debate, compared with 26 percent who felt that Trump did better.