Mr Turnbull won a party room ballot 54 votes to 44 last night, less than six hours after announcing he would challenge Mr Abbott.
The ballot also saw Julie Bishop elected as deputy leader over Kevin Andrews 70 votes to 30 — keeping the position she has held since 2007.
Mr Turnbull, who will now become Australia's fourth prime minister in two years, spoke to reporters outside his apartment this morning.
"It was a long night, and it's going to be a big day today," he said.