Luke Prosser smashed home an injury-time equaliser for Southend to dent Port Vale's League Two play-off hopes.
Rob Taylor's unstoppable drive on the half volley put Vale ahead after Doug Loft's cross was only half cleared.
Sean Clohessy had earlier fired against the post for the visitors while Barry Corr's overhead kick came agonisingly close to an equaliser.
Southend did get their goal in stoppage time when Prosser pounced on the loose ball to fire in from close range.
Port Vale are now three points behind 7th-placed Gillingham in the League Two table, while Southend remain in 14th position.
Port Vale caretaker manager Mark Grew told BBC Radio Stoke:
"We said before the game that it's not about playing well, it's about results.
"Lee Collins is distraught, but one mistake hasn't lost us the game today.
"We were individuals and not a team today.
"We've got to take it on the chin and it's a difficult one to take."
Southend United defender Luke Prosser told BBC Essex:
"I don't really get many goals, so I couldn't really have picked a better day for it - right foot as well.
"Great day, the longer it was 1-0 the longer the pressure was on them really.
"We felt we did well, we knew if we stuck at it, we could get something out of it."