The company is trialling the service in its native US, making TV ads available to cable subscribers in Concord, California, according to a report in The Wall Street Journal.
The firm is eager to tap into the more lucrative market of TV advertising, which in the US is worth about $53bn.
At present, the advertising is targeted at customers of Astound Broadband, a division of WaveDivision Holdings. When Astound's customers watch TV, some of the ads they see will have been sold to advertisers by Google and will appear in normal ad breaks.
Currently Google-sold advertising is not targeted at individual households, but it could ultimately lead to viewers watching ads specifically tailored to their demographics and online behaviour.
However, there is a regulatory minefield with regard to how companies can use consumers' personally identifiable information.
Eric Schmidt, Google's chief executive, told analysts in January that the company is experimenting with TV advertising, without offering any specifics.
The Wall Street Journal reported that Google said it was running an "early phase trial... with a small number of partners and advertisers".