Estimated to cost $1m (£640,000) each, the campaign spots will air on CBS, NBC and Fox, in which the democratic candidate is expected to discuss the US economy just six days before the November 4 election.
The start of a baseball World Series game has been moved by 15 minutes so that the ads can be aired simultaneously at 8pm Eastern Time.
Spanish-language network Univision and smaller cable channels BET and TV One will also air the Obama 'infomercial'.
ABC is the only major US network not to air the ad, due to a failure to reach a deal with the Obama campaign.
The move enforces the spending power of Obama over Republican rival John McCain. Obama has spent an unprecedented $230m (£143m) on television advertising in his campaign for the White House, compared to McCain's $84m.
Obama has shattered US election fundraising records, bringing in $150m in the month of September alone. Unlike McCain, Obama chose to raise funds privately, without accepting funding from the federal government.
The half-hour slot comes right before millions of Americans tune in to watch the Philadelphia Phillies try to bury the Tampa Bay Devil Rays in a continuation of game five of the World Series, which was delayed Monday due to rain. Philadelphia leads the best-of-seven series 3 - 1.
Obama, who currently holds an average five-point lead over McCain, has also filmed an appearance on the mock-news programme 'The Daily Show' with John Stewart, which will air tonight as well.
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