Johnny Gat is second in command of the Saints and is the earliest member of the Saints who is still in the gang. After the bank heist that goes awry, the gang is taken hostage by the Syndicate. Johnny escapes and frees The Protagonist and Shaundi, before attempting to take control of the plane.
Shaundi has become more focused on the Saints and her celebrity status in the years since the Saints conquered Stilwater. She has become more determined, and aggressive since the events of Saints Row 2.
Josh Birk is a model and actor, who is working with the 3rd Street Saints as research for the upcoming Saints movie in which he stars as a Saint. Josh Birk accompanies Johnny Gat, Shaundi and The Protagonist during a bank robbery, and sets off a silent alarm. 
Kinzie Kensington is a former FBI agent who joined the 3rd Street Saints after The Protagonist frees her from the Deckers. Thanks to her hacking knowledge, she is very useful to the Saints in their fight against the Deckers.
While working in the FBI she came close to some sensitive information, that worried the Deckers leader Matt Miller. This caused him to worry and forge some fake situation that got her fired from the FBI.
The Luchadores are one of the three Syndicate gangs in Steelport and are led by Killbane. The Luchadores are in charge of the Carver Island district, where they run a number of protection rackets, using their brawn.
The Deckers are the one of the three gangs in Steelport. They specialize in cyber-warfare and are led by Matt Miller.
They are in charge of the Stanfield district, where they own a number of businesses, including a "sinister" fence manufacturer. The gang members are British youths, wearing black clothes with neon blue stripes on them.