Owners Magnox said the workforce was being cut to 357, down from 522 staff, and about 25 agency workers by May.
Earlier this year, it said 1,600 jobs would be lost at 12 sites by 2016.
Anglesey's planned new nuclear power station, Wylfa Newydd, will employ more than 1,000 people once it begins working in the first half of the 2020s.
A company statement said: "When a nuclear power station moves from generation into the next phase of its lifecycle, which is defuelling, a reduced number of staff are needed for operational work.
"This is not unexpected and we've engaged fully with our staff and the trades unions about the planned changes.
"Wherever possible we will seek to make voluntary redundancies, as we have at our other Magnox stations."
A total of 165 jobs will be lost at Wylfa nuclear power station on Anglesey when the plant moves from energy generation to defueling, say bosses.