Sister Julienne is the Sister-in-Charge of Nonnatus House. She is portrayed by Jenny Agutter.
Sister Julienne is always shown to be the voice of wisdom to the other nurses of Poplar, kind and empathetic, she often helps her fellow Sisters and nurses through personal crisis with gentleness and acceptance.
Before she became a nun, Sister Julienne's name was Louise. Her father was in the army, and when Louise was very small, her father moved the family to Aden upon being posted there. Here, Louise grew close to the young son of another army man, Charles Newgarden, who was friends with her father. Until the early 1930s, Louise and Charles remained very close, and it is implied that they were in love and Charles planned to ask her to marry him, but Louise was called to the religious life and she could not resist it. After standing Charles up at the cinema, Louise cuts nearly all ties with him and becomes a postulant. She sends him a letter before cutting off contact.
In Series One, after seeing how Jenny is disgusted with how the people of the East End live, Sister Julienne relates that when she was new to Poplar, she too often found it hard to curb her revulsion, but expresses that the women living in the conditions are the ones that need their help.
In Season Two, Sister Julienne often councils and consoles Sister Bernadette in her doubts and worries about her position in the Order. She never once insists that it is a phase or that it will wane with time. When Sister Bernadette leaves the Order, Sister Julienne is heartbroken to see her go, but lets her go without resentment. When Sister Bernadette, now Shelagh Mannion, expresses her confusion and heartache over not knowing if her former sisters will want to associate with her now that she is Shelagh, the Sister consoles her and tells her she will always be dear to them and if her wedding to Patrick is meant to be, it will happen. On the day of the wedding, Shelagh says Sister Julienne should walk her down the aisle, but the Sister says "You belong to no-one but yourself, and you know exactly where you're going".
In Series Three, Sister Julienne takes a special interest in a young, pregnant woman named Stella Crangle, who is serving prison time. Stella says she has a fiancé who is a sailor and asks Sister Julienne to be her character witness to the prison board, who will determine whether she is permitted to keep her baby. Sister Julienne tries to help by finding the fiancé, but she soon learns he was an invention by Stella. Going before the prison board, Sister Julienne admits that Stella lied, but pleads that it was a misguided effort to keep her baby. Sister Julienne says she feels that Stella can be a very good mother, but the board say unless Stella can find work and a suitable home for herself and baby, her child will be taken away. After calling in a few favours, Sister Julienne manages to secure Stella lodgings and a job at a Mothers' Hospital. Stella writes Sister Julienne a letter after leaving the prison with her son, expressing her thankfulness to the sister and promising never to forget her kindness.
In Series Four, Charles contacts Sister Julienne again under the guise that he wants to make a generous donation to Nonnatus House, as he is very rich and is dying. When they see each other again for the first time in 30 years, Sister Julienne begins to question whether or not she made the right choice in becoming a nun. Sensing that they both are troubled with the thought of what might have been, she and Charles assure each other that no one could know what their life together might have been, or if they would have been as happy as they are in their current lives. After asking how the Sister would like to hear the news that he has died, Sister Julienne tells Charles that she'd rather not hear it at all, but says a letter is how she'd like to find out. At their last meeting, Sister Julienne and Charles watch the film they were going to watch 30 years before. When the Sister gets the news that Charles has died, she is devastated and still lingers with doubt.
In Series Five, the the birth control pill is introduced to the UK and to the midwives of Nonnatus. Dr. Turner first explains the pill to Sister Julienne, excitedly proclaiming that women can now choose when to get pregnant. However, the Sister is less enthusiastic, proclaiming that the pill presents "moral" complications. The Sister fears that with the ability to avoid pregnancy, younger women will start having regular sex before marriage, and thinks that pregnancy should not be controlled in such a way. This sparks a debate among the women of Nonnatus, and creates a bit of tension between Dr and Mrs. Turner and the nun.
Although Sister Julienne extensively questions the pill's effectiveness and safety, Dr. Turner assures her that it is very effective and very safe.
She accompanied other sisters and nurses on their way to South Africa in the 2016 Christmas Special.
At the start of Series Six, Sister Julienne is demoted following her return from South Africa, and Sister Ursula is made in charge. However, Sister Ursula instates a 20 minute-per-patient rule and Barbara, distracted by the time limit, doesn't notice that a newborn is suffering from carbon monoxide poisoning. After this, Sister Ursula is deemed unfit to run Nonnatus House and Sister Julienne is re-instated to Sister-In-Charge.
In the 2018 Christmas Special, Sister Julienne is summoned back to the Mother House when Mother Jesu Emmanuel, the Mother Superior of the Order, is found to be terminally ill. Sister Julienne fears that she will be elected the new Mother Superior when her fellow Sisters cast their votes, but is relieved when Sister Mildred is elected instead, and she is able to return to Nonnatus House.