Isabel Green (played by Maggie Gyllenhaal) is the mother of the Green children. With her husband, Rory, away fighting in World War II, Isabel has been left to raise their three children, Norman, Megsie, and Vincent. Soon, they children are joined by Cyril and Celia Gray, their snooty cousins from the city, and Isabel is at her wits end with her job at a local store, looking after the children, and Rory's brother, Phil, trying to get her to sell the farm as he gambled it away. Nanny McPhee arrives to help her and quickly manages to bring the children under control.

During a picnic, Phil hands Isabel a telegram which tells her Rory has been killed. However, Norman is convinced his father is alive as he can "feel it in his bones", something he apparently has inherited from Rory, so while he goes to London with Cyril and Nanny McPhee to talk to Cyril's father, who is very high up in the War Office, he leaves Megsie a note, telling her to keep Isabel from selling the farm. Megsie and Celia do everything they can to stall for time. In the meantime, Norman and Cyril find Rory is actually "missing in action", and their is no record of a telegram being sent to Isabel, Norman, Cyril and Nanny McPhee race back to the farm where an enemy pilot has accidently dropped a large bomb in the barley field, and Phil is scared, thinking the bomb is a sign that hit-women, Miss Topsey and Miss Turvey, are coming after him. When Norman and Cyril return, Norman reveals that Phil forged the telegram which announced Rory's death, and Phil actually admits it. Isabel leaves Phil handcuffed to the cooker.

The children succeed in defusing the bomb with the help of Mr Edelweiss, Nanny McPhee's putty-eating jackdaw, who then lets out an almighty burp which flattens the barley and saves Phil from Miss Topsey and Miss Turvey, who had arrived at the farmhouse to punish Phil for failing to give them the deeds to the farm. When Nanny McPhee leaves, she gives Isabel and the children her medals, with Isabel receiving the medal for Leaps of Faith. Seeing Nanny McPhee leave, they take off after her, only to be greeted by a returning Rory, whose left arm is in a sling. Nanny McPhee watches the happy reunion from the top of the hill and smiles before departing.

Green family
Isabel Green, Rory Green, Norman Green, Megan Green, Phil Green, Vincent Green