The 25-year-old returns to Griffin Park after a successful loan spell, putting pen-to-paper on a three-year contract for an undisclosed fee.
A product of Rovers' Academy, Judge had loan spells with Plymouth Argyle and Notts County earlier in his career, before joining the Magpies in January 2011. He was an instant hit at Meadow Lane, winning the Player of the Year award for County in 2011-12 and named in the PFA League One Team of the Year for 2012-13.
The midfielder was one of Gary Bowyer's first signings as manager last May, but was restricted to just 12 first team appearances on his Rovers return. He opted to join League One outfit Brentford at the turn of the year in search of regular first-team football.
It would turn out to be a successful switch, with Judge playing a key role as the Bees clinched automatic promotion to the Championship. The Irishman scored the decisive penalty in a 1-0 win over Preston North End to secure their place in the second tier of English football.
In total, Judge made 22 appearances for Brentford, scoring seven goals, prompting Bees boss Mark Warburton to return for his services.