The channel was part of Playboy Enterprises, founded by Hugh Hefner.
Ofcom has fined Playboy TV £22,500 for broadcasting unencrypted explicit "adult material".
It said the channel had broken rules on broadcasting adult content by showing seven late night shows unencrypted on free-to-air channel Playboy One.
The media regulator said the fine was for the "explicitness of content, strength and/or sustained nature of the sexual content and language".
Playboy One has since been replaced by a new encrypted pay-to-view channel.
The channel was part of the Playboy Enterprises company, founded by Hugh Hefner.
Ofcom received five complaints that the explicit material was inappropriate.
Seven late-night programmes shown at the end of 2007 were investigated.
Titles included Sexy Girls Next Door and Blue Collar Babes.
In its report, Ofcom said the company had failed "to provide enough protection for viewers from harmful or offensive material".
Playboy Enterprises said it was "toning down the content of the channel over time to fall well within Ofcom guidelines".