Lee Bradbury's first-half thunderbolt gave Southend their first Championship away win and heaped more misery on stuttering Cardiff at Ninian Park.
Bradbury blasted home strike partner Freddy Eastwood's knockdown from 20 yards midway through the first period.
Cardiff defender Glenn Loovens hit the bar from Willo Flood's corner, who then forced a fine save with 20-yard shot.
Bradbury went close to adding a second for Southend, before Andrea Ferretti hit the post for Cardiff with a header.
"We'd not lost in our last four away games but now this result gives us that little bit of hope.
"Lee had not scored for 11 games but he worked hard and it was a fantastic strike and I'm very pleased for him.
"It's always tough when you're on a losing run and we hadn't won for 17 games away, and the longer it goes on the tougher it gets.
"You have to target every single game you play but we knew if we started well and got the first goal we had a chance of hanging on and getting a result.
"Now perhaps that might give these players a lift to go on and pick a few more wins away from home."
"We've got to keep working hard and believing we can do it. Our strikers need to start picking their socks up and start banging them in again.
"There's no point putting balls in the box if there's no-one on the end of it. We had enough chances but we've had a lapse of concentration at the back and a sloppy goal but we should still have gone on and won.
"We're still three points off fourth spot after a dreadful run in terms of winning games and we're still hanging in there."
Cardiff: Alexander, Gilbert, Purse, Loovens, McNaughton (Whittingham 52), Flood (Glombard 82), McPhail, Scimeca, Ledley, Chopra, Campbell (Ferretti 26).
Subs Not Used: Forde, Johnson.
Southend: Flahavan, Hunt, Barrett, Clarke, Hammell, Gower, Maher, Guttridge, Campbell-Ryce (Hooper 68), Eastwood (Francis 85), Bradbury (Harrold 86).
Subs Not Used: Welch, Sodje.
Goals: Bradbury 23.
Att: 13,822
Ref: S Tanner (Somerset).