Coleg Menai in Bangor, north Wales, said it refuses to be associated with the "abhorrent" politics of the far-right BNP.
The independently-run National Centre for Language and Culture, Nant Gwrtheyrn, in Gwynedd, has also asked for its details to be removed from the site.
The BNP's website urges people to learn the Welsh language, claiming that "unless the floodgates to Britain are closed or greatly restricted" Welsh will die out in the streets.
"The humble refugees will in no time claim Welsh language and culture to be insulting to them and there (sic) religion, withdrawing such teachings from schools and eventually abolished altogether," it says. It describes the two colleges as being centres for the Welsh language and gives details of courses at Coleg Menai, and the phone number and email address of Nant Gwrtheyrn.
Both organisations are angry at appearing on the site and say they were not consulted.
"Coleg Menai wouldn't wish to be associated in any way with the BNP," said a college spokesman. "The BNP's politics are abhorrent to all of us in the college community.
"We, like all colleges, operate in a spirit of equality and respect for all human beings. We cannot control the actions of these people with regards to their website, but we can confirm that we are seeking legal advice regarding their actions."
Aled Jones-Griffith, chief executive of Nant Gwrtheyrn, said: "We have never been asked to be associated with that particular party. We are an apolitical organisation and therefore we haven't asked to be associated with any party, but definitely not with a party which actively promotes racism and fear of foreigners. We will be contacting the BNP to ask if it will remove our details from its website."
In response to complaints from the colleges, the BNP has published a disclaimer on the site saying that its "support for their work should not be taken in any way to suggest that we believe that they have any sympathy for the British National Party".
But the party has so far refused to remove the colleges' details. A BNP spokesman said: "I think there's something wrong with them if they are upset by the fact that their phone number and address is placed elsewhere."