Schmidt told the Wall Street Journal that the campaigning move was a natural progression, but that he was undertaking it personally and not on behalf of Google, which officially remained neutral.
Schmidt has earlier advised the Obama campaign team on technology and environmental issues and the Wall Street Journal reports that the new campaigning role signifies his push for a greater voice in politics.
Google is starting to face up to life in its position as a hugely influential corporation rather than a friendly start-up company. It recently felt the impact of political influence when lobbyists said that they objected to an advertising deal it was doing with Yahoo! because they feared a monopoly.
Google has also lobbied the government on telecoms and broadband internet issues.
Schmidt has denied that this is his motivation for joining the Obama campaign, telling the WSJ: "My sense is, the Justice Department makes judgments on these issues [such as monopolies] independent of politics.
"It would be unfair to justice to imply [that supporting Senator Obama] would make a difference."
Campaigning on Obama's behalf could be a dangerous move, should the Republican party win the election, but polls are predicting victory for the Democrats in just 14 days time.