Goals from Megan Connolly and Inessa Kaagman were enough to seal three points for the hosts.
Despite Brighton taking the points, there was no difference in quality with both sides evenly matched across the pitch.
Carla Ward’s first competitive team selection saw debuts for Jamie-Lee Napier, Christie Murray, Chloe McCarron and Georgia Brougham. Destiney Toussaint was also on the bench.
Blues started the game positively, with new signing Napier seeing plenty of the ball down the right-hand side.
The first chance of the game came the way of Claudia Walker. She cut the ball inside of her marker before seeing her low drive blocked by Rebekah Stott.
Brighton came close to opening the scoring through Kaagman. The midfielder’s long-range effort was tipped onto the crossbar by Hannah Hampton.
The home side again struck the crossbar midway through the half when Dani Bowman’s free-kick beat Hampton.
After big chances for Brighton, Ward’s side settled for the remainder of the half playing the ball out from the back and looking for the wingers to create the play.
Birmingham, sporting the red away kit, started the second half as they closed the first. Steady play and searching for the right passes to build attacks, with Murray the focal point in midfield.
Despite positive play from Blues, the hosts took the lead. Connolly took aim from 25 yards and found the top right-hand corner.
Brighton doubled their lead minutes later. Ria Jarrett fired a cross into the box, where Kaagman was waiting to head it in.
Toussiant came on her debut late in the game as Blues searched for a way back into the game.
Despite an opening day defeat, there were plenty of positives that came from the game that Blues can build on for the rest of the season.
Next up, Birmingham take on Manchester United in our first home game of the season on Sunday 13thSeptember, kick off 2pm.