The Alliance leader described an emotional election campaign.
Ms Long topped the poll in East Belfast with 8,195 votes and was elected on the first count in the constituency.
She described an emotional campaign and revealed her father-in-law’s funeral had taken place on polling day.
“It’s been quite an emotional election campaign for me. I lost my father-in-law in the last few weeks, and we buried him yesterday,” she said.
“I just want to dedicate this win to him because without family I could not do what I do, and without their support, I would not be where I am.”
Looking ahead to the rest of the election count, she said she is looking forward to seeing more of her party’s candidates elected, including her East Belfast running mate Peter McReynolds.
Alliance previously held two seats in East Belfast with Ms Long and Chris Lyttle who stepped aside.
“It’s been a good day so far for Alliance and obviously it’s been a good day for me personally in East Belfast and also for Peter McReynolds and we expect that we will hold the two seats there,” she said
“I am just absolutely thrilled that I’ve polled so well and I really look forward to later on today and seeing all my colleagues bringing it home.
“It’s good that in my own constituency we were able to poll such a strong vote, and I think it just shows that East Belfast is a positive constituency. We want a progressive future.
“We’re the constituency where Stormont sits but we want to see it working and I think that’s a really strong message.”