He spent last season on loan at Cardiff City and Burnley and will replace Shaun Goater in the Shrimpers attack following the Bermudan's retirement this summer.
Ricketts, who was capped once by Sven-Goran Eriksson against Holland in 2002, has not been a success at Leeds, returning only 2 goals in 29 appearances for the Whites.
Southend chief executive Geoffrey King told their official website: "We're understandably delighted to have signed Michael as we believe he will be a great acquisition for Southend.
"Shaun Goater proved last year what an experienced face can bring to the side and we hope Michael will prove just as successful.
"It's important that we make the right signings and both Steve Tilson and Paul Brush believe Michael has the right qualities."