She topped the poll in East Belfast and was re-elected on the first count, along with Joanne Bunting (DUP).
Ms Long secured 8,195 first preference votes, while Ms Bunting polled 7,253.
Ms Long told the media: “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.
“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. 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.
“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.”
Next in line for a seat as the count progresses in David Brooks of the DUP with 6,633 votes.
Peter McReynolds of Alliance is likely to claim a second seat for the party having polled 5,820 votes – ahead of the Ulster Unionist’s Andy Allen on 5,281.
The TUV vote was up by 4.9% of the total share as John Ross polled 3,087 (7.1%).
The DUP’s total share of the vote was 32.1% (down from 37.6% in 2017).
Alliance was narrowly ahead of the DUP in terms of the total vote on 32.4% (up 1% on 2017).