The 34-year-old, who also had spells with Watford, Leeds United, Birmingham City and Stoke City, left Bury in May.
The Essex club, who play in the seventh tier, also signed former Republic of Ireland and Wolves defender Kevin Foley, 32, on Monday.
They join ex-Premier League pair Paul Konchesky and Jamie O'Hara at the club, who play in the seventh tier.
Former England defender Konchesky and ex-Tottenham midfielder O'Hara joined the ambitious side - who play three divisions below the English Football League - last season.
As well as Pennant and Foley, the club have also announced the signing of former West Ham United youngster Leo Chambers, 22.
Billericay owner-manager Glenn Tamplin recently revealed he has spent £2m on the club since taking over in December 2016, as he aims to reach the EFL within five years.
Pennant played in the 2007 Champions League final for Liverpool, while Foley made 175 league starts for Wolves between 2007 and January 2015.
Find all the latest football transfers on our dedicated page.
Former Arsenal and Liverpool winger Jermaine Pennant has signed a two-year deal with non-league Billericay Town.