Sister Winifred is introduced at the beginning of Series Three. She is portrayed by Victoria Yeates.
Sister Winifred joined Nonnatus House after taking her vows at the Mother House. A warm-hearted, slightly innocent young woman, she has lived most of her life in the countryside. She has only recently qualified as a nurse and a midwife and is still to find her feet. She has mainly practiced in a small cottage hospital in a rural town and is shocked by the deprivation that greets her in the East End.
Her grittiest work to date has been a stint as a Department of Education Head inspector (nit nurse).
After being at Nonnatus House for over a year, Sister Winifred grows in confidence and has become a trusted member of the community.
It is not known wether Winifred was her birth name or the name chosen when she entered the Order.
She is the same age as Jenny, Trixie and Cynthia. Prior to coming to Nonnatus House, she was already familiar with Sister Evangelina, whom she met on Evangelina's summer holiday at the village school. She reveals that she previously worked as a head inspector, or a nit nurse, which led to the children nicknaming her "Nitty Nora the Scalp Explorer", probably because there aren't many things that rhyme with Winifred. Before becoming a nun, nurse and midwife, Sister Winifred was a teacher, and loved her job greatly.
At the beginning of her stay at Nonnatus, Sister Winifred is shown to be uncertain of midwifery in general, later telling one of the other nurses that she doesn't get the same feeling of joy out of it as the others do. She also is shown to be uneasy helping women give birth, unsure of herself and saying less than helpful things. However, after being left to help a young Jewish woman give birth, Sister Winifred finds the strength and courage to deliver the baby and comes to enjoy midwifery.
In Series Six, Sister Winifred asks Nurse Crane to teach her how to drive. In the first episode of Series Seven, Sister Winifred passes her driving test.
In the 2018 Christmas Special, Sister Winifred returns to the Mother House with Sister Julienne and the newly-arrived Sister Mildred after the Mother Superior becomes terminally ill. While there, Sister Winifred admits that she wants to stay at the Mother House and work with the children at the orphanage in spite of her vow of obedience. Also, Sister Julienne is expected to be named the new Mother Superior, but Sister Mildred is elected instead, and she requests that Sister Winifred remain at the Mother House to work with the children, and Sister Winifred cannot hide her delight.