West Brom took the lead in first-half stoppage time when Hal Robson-Kanu headed in Kieran Gibbs’s cross.
Homegrown midfielder Sam Field converted Matt Phillips's cross after 56 minutes for the 19-year-old’s first Premier League goal.
The hosts looked on course for a first win since August but were undone by two Matt Ritchie set-pieces.
Ciaran Clark headed in a corner on 59 minutes before Ritchie’s 83rd-minute free-kick deflected in off Evans, ending Newcastle’s run of four successive Premier League defeats.
West Brom: 2 Dec v Crystal Palace (H)
Newcastle: 2 Dec v Chelsea (A)