Members of the University and College Union (UCU) are taking part in a two-day national strike which is happening at universities across the UK.
UCU members in Wrexham formed a picket line at the university's main entrance on Mold Road on Wednesday as members also showed their support via placards outside the main building in Cardiff.
University employers have described the decision to strike as "disappointing".
The union said the 1.1% pay rise offered by the universities was "an insult".
Staff are refusing to set extra work, cover for absent colleagues or work overtime on Wednesday.
If no agreement is reached, members have agreed to further strike action targeting open days and graduation ceremonies in June and July.
The union is also beginning preparations for a boycott of the setting and marking of students' work, to begin in the autumn.
Universities and Colleges Employers Association (UCEA) said the offer was "at, and, for some, beyond, a limit of affordability for higher education institutions and the very best offer that will be available this year".
UCEA maintained the weighting of the offer meant the worst paid university staff would get a rise of more than 5%.
Universities in Wales are staging a walk out in a row over pay.