Vice Media plans to shrink its workforce by as much as 15% through attrition and cut its selection of digital sites by at least half, according to people familiar with the matter, as growth stalls at the onetime new-media darling.

Revenue at the Brooklyn-based company is expected to be roughly flat this year, the people said, coming in between $600 and $650 million, on par with 2017. That number is more than $100 million below the projection Vice offered private-equity firm TPG in the summer of 2017. TPG’s investment gave...