Murray, who won Team GB's 65th and final medal at London 2012 last summer, placed seventh, French tenth, her highest senior finish, and Spence 12th - but together it was good enough for victory in the team event.
That took Britain's medal tally in Poland to three with Murray and French part of the women's relay trio, along with Katy Burke, that won gold while bronze was claimed in the men's equivalent.
Meanwhile Freyja Prentice just missed out on an individual medal, coming home fourth in Poland at her first major competition since recovering from a hamstring injury.
French breaks world record in modern pentathlon World Cup return
Pentathlon GB performance director Jan Bartu said: "They dominated the team competition, everything went for them. It was a really well deserved gold medal and a very positive experience for them.
"An individual medal didn't happen, but the competition was really stiff. It was a very successful day and a good stepping stone for the World Championships."
GB’s Choong and Cooke finish without a medal in modern pentathlon
GB women end winning run in Olympic modern pentathlon competition