Pawlowska steadily accumulated points on the intermediate sprints that are the feature of the 100-lap race, edging Canada's Jasmin Glaesser into the silver medal position. Cuba's Arlenis Sierra Canadilla was third.
The Pole won the scratch race title in 2012 and 2013.
Ireland's Caroline Ryan suffered a heavy crash near the end of the race and was taken off the track on a stretcher after receiving medical attention.
Katarzyna Pawlowska crowned world champion for third time
It was not immediately clear how bad the injury was.
The highlight of the penultimate evening of racing will be Olympic sprint champion Jason Kenny of Britain up against Australia's Matthew Glaetzer in the best-of-three final after they convincingly won their semis.
The men's omnium will also conclude with Britain's Mark Cavendish battling for a top-three finish in his bid to earn a place in the 2016 Rio Olympic team.
Cavendish is fifth going into the sixth and final event, the points race. Elia Viviani leads overall.