Crosby, will replace GMTV veteran Fiona Phillips, who announced her departure in September after 15 years.
Emma said: “I am very excited to be joining Britain’s leading breakfast programme and working alongside Kate, who is a great talent.”
Martin Frizell, editor of GMTV, said: “Emma will be joining us in the new year to share front line presenting duties with Kate Garraway.
“Together they will make up the best live presenting team in morning television.”
Both Crosby and McCabe will join in the new year.