McConnell, who leads Republicans in the US Senate, is projected to have won another six-year term in office, judging by a partial count of ballots after polls closed in Kentucky on Tuesday night.
The 78-year-old has sat in the US Senate since 1984 and led Republicans in the chamber since 2006. This will be his seventh term as a senator.
McConnell faced a tough challenge for his seat from Democrat Amy McGrath, a former US Marine Corps fighter pilot who raised an eye-popping $90 million in her campaign, compared to $57.2 million raised by McConnell.