MacFarlane said: "It's truly an overwhelming privilege to be asked to host the Oscars.
"My thoughts upon hearing the news were, one, I will do my utmost to live up to the high standards set forth by my predecessors; and two, I hope they don't find out I hosted the Charlie Sheen Roast."
Telecast producers Craig Zadan and Neil Meron added: "We are thrilled to have Seth MacFarlane host the Oscars. His performing skills blend perfectly with our ideas for making the show entertaining and fresh.
"He will be the consummate host, and we are so happy to be working with him."
MacFarlane directed his first feature film with Ted, also serving as co-writer, producer and the voice of the title character on the project.
The 2013 Oscars will take place at the Dolby Theatre at the Hollywood & Highland Centre in LA and be broadcast live on ABC.