Eddie, 33, memenangi kategori tersebut menerusi watak Stephen Hawking dalam filem Theory of Everything.
Dia mengalahkan beberapa calon lain seperti Steve Carrel, Benedict Cumberbatch, Jake Gyllenhaal dan Michael Keaton.
Prestasi yang sama turut dicapai oleh Julianne Moore dalam filem Still Alice yang menewaskan Rosamund Pike (Gone Girl), Felicity Jones (Theory of Everything), dan Reese Witherspoon (Wild).
Sementara itu, pada acara ini turut mengangkat drama Orange Is the New Black sebagai Drama Komedi Bersiri Terbaik.
Drama tersebut menewaskan lima drama komedi popular lain. Drama komedi itu berjaya mengalahkan Modern Family, Brooklyn Nine-Nine, Veep, dan The Big Bang Theory.
Drama tersebut diarahkan oleh Jenji Kohan, 'Orang Is the New Black' dan ditayangkan pada tahun 2013.
Antara pelakonnya terdiri daripada Taylor Schilling (Piper Chapman), Michael J. Harney (Sam Healy) dan Kate Mulgrew (Galina "Red" Reznikov).
'Orange Is the New Black' menceritakan tentang kehidupan Piper Chapman iaitu seorang lesbian yang dipenjara kerana masalah dadah selama 15 bulan. Sehingga kini, 'Orange Is the New Black' sudah memasuki 26 episod.
Senarai Pemenang Screen Actors Guild Awards 2015
Outstanding Performance by A Cast In A Motion Picture
Birdman
Lifetime Achievement Award
Debbie Reynolds
Outstanding Performance by A Female Actor In A Motion Picture
Julianne Moore (Still Alice)
Outstanding Performance by A Male Actor In A Motion Picture
Eddie Redmayne (The Theory of Everything)
Outstanding Performance by A Female Actor In A Supporting Role
Patricia Arquette (Boyhood)
Outstanding Performance by A Male Actor In A Supporting Role
J.K. Simmons (Whiplash)
Outstanding Performance by An Ensemble In A Comedy Series
Orange Is the New Black
Outstanding Performance by An Ensemble In A Comedy Series
Downton Abbey
Outstanding Performance by A Male Actor In A Television Movie or Miniseries
Mark Ruffalo (The Normal Heart)
Outstanding Performance by A Female Actor In A Television Movie or Miniseries
Frances McDormand (Olive Kitteridge)
Outstanding Performance by A Male Actor In A Drama Series
Kevin Spacey (House of Cards)
Outstanding Performance by A Female Actor In A Drama Series
Viola Davis (How to Get Away With Murder)
Outstanding Performance by A Male Actor In A Comedy Series
William H. Macy (Shameless)
Outstanding Performance by A Female Actor In A Comedy Series
Uzo Aduba (Orange Is the New Black)
