It is the first time Coastal have made it to this stage of the competition and the first time they have played outside the South Island.
It has been one of the club’s most successful seasons since their inception in 2007.
With just five games to go in the Southern League, Coastal sit in second, just one point behind league leaders Cashmere Technical.
They’re also in the semi-finals of the English Cup, where they will play Western AFC in two weeks.
“The club’s obviously chuffed,” said Coastal head coach Robbie Stanton.
“Not just in the Chatham Cup, but also what we’ve done so far this year on the pitch, they’ve been very supportive.”
They upset Northern League side Melville United 1-0 to reach this round, while Coastal needed extra time to beat Ferrymead Bays 5-3.
Cashmere Tech and Nomads will play their English Cup quarter-final on Saturday, which was postponed last month due to a failed floodlight at English Park.
The winner will take the last semi-final spot, playing Christchurch United next month.