Born Rosamunde E. M. L. Scott on 22 September 1924 in Lelant, Cornwall, daughter of Helen and Charles Scott, a British commander. Just before her birth her father was posted in Burma, her mother remained in England. She attended the School of St. Clare in Penzance and Howell's School Llandaff before going on to Miss Kerr-Sanders' Secretarial College. She began writing when she was seven, and published her first short story when she was 15.

From 1943 through 1946, Pilcher served with the Women's Royal Naval Service. On 7 December 1946, she married Graham Hope Pilcher, a war hero and jute industry executive who died in March 2009. They moved to Dundee, Scotland. They had two daughters and two sons, and fourteen grandchildren. Her son, Robin Pilcher, is also a novelist.

In 1949, Pilcher's first book, a romance novel, was published by Mills and Boon, under the pseudonym Jane Fraser. She published a further ten novels under that name. In 1955, she also began writing under her real name with Secret to Tell. By 1965 she had dropped the pseudonym and was signing her own name to all of her novels.

At the beginning writing was a refuge from her daily life. She claims that writing saved her marriage. The real breakthrough in Pilcher's career came in 1987, when she wrote the family saga, The Shell Seekers. Since then her books have made her one of the more successful contemporary female authors.

The Shell Seekers, focuses on Penelope Stern Keeling, an elderly British woman who relives her life in flashbacks, and on her relationship with her adult children. Keeling's life was not extraordinary, but it spans "a time of huge importance and change in the world." The novel describes the everyday details of what life during World War II was like for some of those who lived in Britain. The Shell Seekers sold more than five million copies worldwide and was adapted for the stage by Terence Brady and Charlotte Bingham.

In 1996, her novel Coming Home won the Romantic Novel of the Year Award by Romantic Novelists' Association.

Pilcher retired from writing in 2000. Two years later she was created an Officer of the Order of the British Empire (OBE).

Her books are especially popular in Germany because the national TV station ZDF (Zweites Deutsches Fernsehen) has produced more than 100 of her stories for TV starting with "Day of the Storm". These TV films are some of the most popular programmes on ZDF. Both ZDF programme director Dr. Claus Beling and Rosamunde Pilcher were awarded the British Tourism Award in 2002 for the positive effect the books and the TV versions had on Cornwall and Devon tourism within the UK. Notable film locations include Prideaux Place, an Elizabethan Manor with extensive grounds in Padstow; the 9th century stately home in St Germans, Port Eliot; The Duke of Cornwall Hotel, an 1863 Victorian Gothic building in Plymouth; and much of the coast line of Chapel Porth. However, a number of films whose story setting is Cornwall are in fact filmed elsewhere.

"The Shell Seekers" was made into a 1989 movie starring Angela Lansbury.