Adrian Segecic made sure Watford's dismal away form continued as his 79th-minute equaliser handed Portsmouth a 2-2 draw at Fratton Park.
The Hornets looked to be ending their nine-match winless streak on the road after Rocco Vata had turned around Yang Min-hyeok's early strike with a goal and an assist.
But Segecic jumped off the bench to beat Egil Selvik at his near post to share the points and keep some pressure on Watford boss Paulo Pezzolano.
South Korean Yang hung around in the middle for Marlon Pack's long throw to be abysmally defended by the visitors and land at his feet to stroke home his first Pompey goal in the fifth minute.
Watford responded quickly with a long throw of their own, but no one gambled in the middle to tap in after Vivaldo Semedo had poked past the goalkeeper.