Avella received 52 percent of the vote for the 11th Senate District, which includes Bayside, parts of Flushing, Fresh Meadows, College Point, Whitestone and Little Neck.
He was the projected winner as of Wednesday morning, with 95 percent of his precincts reporting.
Liu — who ran for mayor in 2013, losing in the primary — picked up 47 percent of the votes.
The New York Observer, reporting Tuesday night from Liu's election party in Bayside, said he told his supporters that "every vote must be counted."
“It’ll be a few days, if not a week or so to get the results," he said.
The race was close with Avella winning by fewer than 600 votes.