The 17-year-old stopped halfway into her fourth song and told a near capacity Challenge Stadium audience she needed to take a moment and went backstage.
Lorde was forced to reschedule her Australian tour in April on doctor's advice.
"Perth, I'm so sorry, can you give me one minute? I'm just not feeling very well," she said.
A man appeared on stage a few minutes later explaining there were "technical issues".
Lorde reappeared five minutes later, again apologising before restarting the show.
"I must have eaten something weird," she said.
"I've never had to do that. I love you and I'm so grateful to be here."
The mishap didn't seem to slow down the New Zealand teenager who jumped right back into her set.
But about 40 minutes later, after performing her 2013 smash hit Royals, the singer took a moment to wrap a towel around her neck and crouch next to a fan, saying she "just felt tired".
Lorde told the crowd she was disappointed she had to reschedule her previous Australian tour and thanked those who "rescheduled a work shift"or had to "catch a bus"to attend the concert.
Lorde has seven more shows in Australia before a 22-date United States and Canada tour in August and September.
Earlier in the day Lorde had tweeted: "Holy s*** Perth I am way too excited for this show!!!"
