Boss follows Chicago's Mayor Tom Kane (Grammer), who hides his degenerative neurological disorder from his colleagues and those close to him, except for his neurologist (Karen Aldridge).
The Starz series, which began airing last year with eight episodes, will be back for a second run on Friday, August 17.
Boss stars Martin Donovan, Kathleen Robertson, Jeff Hephner and Connie Nielsen as Kane's wife, with Hannah Ware as his daughter.
The second season will also see the return of Jonathan Groff as Kane's ambitious young advisor and Sanaa Lathan as Kane's chief of staff.
Elsewhere, rapper TI will portray an ex-gangbanger with hopes for a political career.
Watch a teaser of Boss's second season below (US only):