Nigeria will face Germany, which beat France 2-1 in the other semi on Wednesday in Montreal, in the championship match on Sunday.
Oshoala scored in the 24th minute to give Nigeria a 2-0 advantage, and added her other three goals in a 25-minute span in the second half. Courtney Dike and Uchechi Sunday also scored for the winning side.
Jon So Yon, on a penalty kick in the 62nd minute, and Ri Un Sim replied for North Korea. The North Koreans will play France in the third-place match on Sunday.
At Montreal’s Olympic Stadium, Lena Petermann’s goal in the 81st minute stood up as the winner as Germany edged France in the later semifinal match.
Pauline Bremer scored in the 12th minute to give Germany a 1-0 edge, but Griedge Mbock Bathy replied for France to tie the game in the 45th.