Rangers led 1-0 at halftime, but Southern fought back to level the scores early in the second half.
However, a couple of late Southern errors gave Rangers the space to find the back of the net and run away with the win.
It was a tense, physical encounter for the teams in their first national league conrt4sencounter against each other.
Southern coach Kris Ridley said his side’s game plan worked in moments, but Rangers threw everything they had at them.
"It worked for them today, but we just gave the ball away a little too many times and then execution," Ridley said.
"Happy with the effort of the girls — they definitely tried to get the win.
"It’s always hard coming from behind."
Defender Marissa Porteous, who played for Southern last season when Rangers failed to qualify for the national league, opened the scoring.
She climbed high from the corner to tuck away a nice header and give Rangers a 1-0 lead.
Southern held most of the possession early in the second half and found their breakthrough soon.
Danica Urlich-Beech brought the ball into the box, had a couple of touches to settle through Rangers’ defence and controlled it nicely to finish.
Porteous then set up Shannon Henson for her first.
She banged a wild cross into the box that Henson headed home to regain a 2-1 lead in the 73rd minute.
Henson connected another header from a corner to cement the win.
Phoenix Reserves grabbed their first win of the season, beating Central 5-0.
Waterside Karori defeated Canterbury United Pride 3-2, Auckland United downed Wellington United 2-0, and Western Springs lost 3-1 to Eastern Suburbs.
Southern are back home to the Phoenix Reserves on Saturday.
National league
The scores
West Coast Rangers 3
Marissa Porteous 41’, Shannon Henson 73’, 86’
Southern United 1
Danica Urlich-Beech 56’,
Halftime: Rangers 1-0.
