The finance committee of the CSU Board of Trustees approved the hike, which would be the second fee increase that students at the 23-campus system will have to endure this fall.
The full board voted on the proposal Tuesday afternoon and approved it.
Cal State students were expected to protest the tuition increases.
The hikes are a result of California Gov. Brown's budget, which was just signed into law recently.
CSU officials said their budget, which was cut back by $500 million back in January, is now being cut an additional $150 million.
The 12-percent increase will be added to an approximately 10-percent fee hike that is already going to go into effect later this year.
Enrollment could also be cut in the winter and spring terms. Employee layoffs are being considered as well.
University of California officials will consider a fee hike on Thursday. UC officials are considering a 9.6-percent hike, which will be added to a 10-percent increase that's taking effect in the fall.
Both university systems are promising additional financial aid in light of the tuition increases, but student leaders say it's still unfair. They said they've been dealing with fee hikes for over a decade, and pointed out that it now costs three times as much to attend a CSU or UC school.