The side overcame a halftime deficit and held on to claim a 2-1 victory over Waitakere United at Forsyth Barr Stadium.
Goals to Conor McDonald and Garbhan Coughlan put it ahead, before Andrew Abba rattled the crossbar in the 93rd minute for the visitors.
Southern was able to scramble the ball away though, notching its fifth win of the season.
It was made to work hard for it however, and it was Waitakere which had the better chances early.
Southern dominated possession through the first half, but struggled to create anything meaningful.
The visitors were energetic and their defence picked off Southern’s passes when it played through the midfield.
Waitakere was unable to hold the ball for long itself, although was more lively when it did get it.
Abba was a constant threat up the right wing.
He missed two he should have put away, but slotted the third from a tight angle on the right in the 39th minute.
Around the same time Southern began to create more.
It drew two great saves from Waitakere keeper Nick Draper, who was outstanding all day.
Waitakere had the better start to the second half too, although Southern eventually gained dominance.
It looked to play more directly and get its dangerous attackers running on to long balls.
Ben Wade added spark on his introduction, while Coughlan and Abdulla Al-Kalisy were more lively in the second half.
McDonald, on debut having recently transferred from Cliftonville in Northern Ireland, equalised in the 64th minute.
A nice build up put him in space and allowed him to find the bottom right corner from just outside the box.
Southern continued to attack and it took another diving save from Draper to prevent Tony Whitehead making it two.
He could not stop Coughlan two minutes later, though.
The striker was put into space by a ball over the top from Al-Kalisy, leaving Draper to drag him down in the box.
Coughlan converted from the spot — his 10th goal of the season.
Abba had another chance late, before a header from a corner hit the crossbar deep in added time.
Southern coach Paul O’Reilly said it was a case of "winning ugly".
"It was probably one of our poorer performances.
"We just struggled to get going — the first half in particular we struggled.
"Although we had a couple of clear cut chances they definitely were the better team in the first half and we were probably lucky to be at 1-0.
"It was unlike us, we looked lethargic — looked like it was hard work today.
"But still massive resolve to come away with a positive result at the end of it.
"That’s the type of result that you need to grind out duringthe season."
The win takes Southern to 17 points, leaping Hawke’s Bay United in the process.
National premiership
The scores
Southern United 2
Conor McDonald 64’, Garbhan Coughlan 77’.
Waitakere United 1
Andrew Abba 39’.
Halftime: 1-0
