The Totally Jodie Marsh show prompted complaints over swearing
MTV has been fined £255,000 by watchdog Ofcom for broadcasting offensive language before the watershed.
The broadcaster was censured for "persistent" breaches on some of its European channels on programmes that were likely to appeal to children.
Reality shows repeated during the day contained swearing and music videos not suitable for children were shown before 2100, the media regulator said.
MTV blamed the mistakes on human error and technical problems.
A spokesman for the broadcaster said: "We take this sanction and fine very seriously."
He added that the network had taken "a series of steps to minimise as much as possible any breaches in the future".
Ofcom concluded that the material breached regulations because it was "not justified by the context of the broadcasts".
They added that the network had agreed to implement a six-point plan to address their failings.
Totally Jodie Marsh - a reality programme shown on the TMF channel in the UK - prompted a number of complaints because of the model's use of bad language.
Ofcom said in a statement: "Pop video and entertainment channels like those controlled by MTV Networks attract large numbers of viewers under 15.
"They have a responsibility to these children and their parents to ensure their compliance arrangements are robust and effective."
TMF was also criticised for playing the video to Windowlicker, a track by dance producer Aphex Twin, which contained repeated swearing and also attracted complaints.
And the network's viewer-based text message show Mr Know It All came under fire for screening sexually explicit content.
Ofcom concluded that the material contained in the text messages was "grotesque, unpleasant and offensive".
MTV France's text programme Belge Chat fell foul of broadcasting regulations by showing a series of racist and homophobic comments, the regulator added.
The continental station was fined £35,000 of the total fine while MTV UK and TMF were hit the hardest with penalties of £80,000 each.
MTV Hits was handed a fine of £60,000 to make a total of £255,000 across the network.