Hannah Porter and Karissa Rodney got on the scoresheet for C&K in normal time before Paige Wakefield claimed the extra-time winner at AFC Hornchurch’s Bridge Avenue Stadium.
And manager Steve Tilson was delighted to see his side come out on top and be crowned County champions once again.
Tilson said: “It was entertaining to the death!
“If you don’t put your chances away it can be costly and, whenever a game is tight, at whatever level, both sides are going to keep going. Fair play to Billericay, who really made it difficult for us.”
“We scored three decent goals. Our girls did well. At the end of the day it’s a cup final and there was a really good atmosphere. It was a great advert for women’s football.
“We always say before each season that we have two aims - to improve our league position and to win the County Cup. We have achieved both of those and we’ll look to do the same next year, but you can take anything for granted, as tonight’s game has proven.”
C&K started brightly but fell behind inside nine minutes thanks to a Paris Smith header.
But Billericay’s lead lasted only eight minutes as Stacey Little, a winner of the competition with West Ham United, headed the ball on to Hannah Porter who found the back of the net.
C&K took the lead two minutes before half time as Karissa Rodney directed an Amy Nash cross beyond Billericay goalkeeper Robyn Strauss.
But Billericay were not to be behind for long as Haley Piggott found the roof of the net soon after the interval.
Strauss denied Sara Sinclair and Angela Addison before Rodney struck the crossbar as C&K went in search of a winner.
But with extra-time looming, neither side was able to produce another goal.
Zoe Rushen came close to putting C&K back in front in the first period, but her free kick came back off the woodwork and Wakefield’s shot from the edge of the penalty area went just wide.
In the second half, Rodney hit the inside of the post and saw her strike roll agonisingly across the line before being cleared.
The match looked destined to go to penalties but Wakefield headed home a Nash cross with eight minutes remaining for C&K to be crowned Essex County Cup champions for the fourth time in five seasons.