The 40-minute Xmas edition will air later this year, while filming for the next series will begin in 2013.
Centred around the Brockman family, Outnumbered follows parents Pete (Hugh Dennis) and Sue (Claire Skinner) as they struggle to control their unruly children Jake (Tyger Drew-Honey), Ben (Daniel Roche) and Karen (Ramona Marquez).
There had previously been rumours that the programme may not get a fifth series with reports claiming that the show would only return with one-off specials.
Created by Andy Hamilton and Guy Jenkin, the show won the National Television Award for 'Best Comedy' earlier this year.
The most recent Christmas special of Outnumbered pulled in over 8 million viewers for BBC One on Christmas Eve.
Watch a clip of Outnumbered doing Sport Relief below: