Welsh-language broadcaster S4C informed Ofcom in July this year that it intended to cease provision of S4C HD on Freeview in Wales on December 1, 2012.
As this capacity is reserved for public service broadcasters, Channel 4 informed the regulator that it wanted to provide HD services to Welsh audiences.
Channel 4's proposal to replace S4C HD with the Channel 4 HD network on Freeview in Wales was agreed last month, and will now go ahead on December 1.
This means that Welsh homes with Freeview HD will be able to watch live Channel 4 programmes in HD, such as Hollyoaks, hit drama Homeland and factual entertainment show Hotel GB.
A Channel 4 spokesperson said: "We're delighted we have been successful in our application for S4C's Freeview HD capacity in Wales. This will enable us to further expand the reach of our Channel 4 HD service."
It is likely that viewers will need to retune their Freeview equipment after Channel 4 HD launches in order to access the new network. More details on this are expected to follow shortly.