The England U-17 and U-23 international was part of the Reading side which secured the FA WSL 2 title in 2015, gaining promotion to WSL 1.
The former Arsenal midfielder played a key part in the title winning season, scoring five times in 12 league appearances, as well as finding the net twice in four cup appearances.
In the same season, the 23-year-old was also part of the team who narrowly lost 3-2 to Notts, on the way to the Lady Pies reaching the Continental Cup final.
On signing the deal, Bragg told nclfc.co.uk, “I’m delighted to sign for Notts County and I’m very excited to get started. I feel like I’ve got a lot to offer the team and hopefully I can have a big impact on a successful season.”
Manager Rick Passmoor added, “Bianca adds fantastic depth to our squad and despite only being 23, she already has a great amount of experience in the WSL which will be a big benefit to this football club”
Bragg will be eligible for selection for this Sunday’s SSE Women’s FA Cup 5th round tie against Yeovil Town.
