Milutin Osmajic scored two goals to help Preston secure a 2-1 victory against Watford, with North End boss Paul Heckingbottom being sent off during half-time.
Despite Rocco Vata's late goal, it was the third consecutive home defeat for Watford. Preston, who won only their second away game this season, deserved the win.
Watford suffered an early setback when winger Kwadwo Baah got injured during an attack and was replaced by Festy Ebosele in the 14th minute.
Preston took the lead in the 17th minute when debutant Jayden Meghoma set up Osmajic for a goal after dispossessing James Abankwah just outside the box on the left.
Although Watford came close to conceding again, with Kaine Kesler-Hayden posing a threat on the right, they were saved by Francisco Sierralta's goal-line block.
Preston's dominance was evident, but Heckingbottom received a red card at half-time for his comments towards the officials in the tunnel.
Osmajic continued to trouble Watford's defense and scored his second goal in the 56th minute, outrunning Yasser Larouci before beating the keeper with a strong shot.
Despite some attempts from Watford, including a goal from Vata, Preston managed to hold on to their lead during seven minutes of added time.