One Nation has won its first lower house seat in Western Australia after candidate Luke Herdegen defeated Labor's Georgia Tree in the Secret Harbour by-election. The result is a historic breakthrough for Pauline Hanson's party, marking its first-ever seat in the WA Legislative Assembly and signalling growing momentum for the party in state and territory politics.

As of Sunday morning, Herdegen had secured 57.04 per cent of the two-candidate-preferred vote against Tree's 42.96 per cent. Labor's primary vote collapsed to 24 per cent, down sharply from the 46 per cent it won in the 2025 WA state election, underlining a significant swing away from the governing party in the seat.