About 30 protesters refused to leave Pantycelyn at the end of term on Sunday and five climbed on the roof on Monday.
The campaigners said they would also go on hunger strike on 21 June, the day before a decision is due on whether the accommodation will close indefinitely.
The university recommended the halls close to make them "fit for purpose".
It said the building would still be used for Welsh language services.
But campaigners have accused the university of not placing enough value in the Welsh language.
Student Bethan Roberts said: "We are here occupying the building with students and people from all over Wales to ensure this stays as a Welsh halls of residence."
Students at Aberystwyth University have climbed on the roof of a Welsh language hall of residence to protest its proposed closure.