Santosh Shailja was born on 14th April, 1937 in Amritsar (Punjab). She had her education upto Matriculation there. After that her parents shifted to Delhi where she did her B.A. and M.A. (Hindi). After doing her B.Ed. she taught in Govt. Higher Secondary School in Delhi. After marriage with Shri Shanta Kumar in 1964, both came to live in Palampur, Himachal Pradesh. She is blessed with three daughters and a son. All are married and blessed with children.
As she had an aptitude for reading and writing, her first story appeared in Panchjanya, a Hindi weekly from Delhi. Afterwards, she regularly wrote stories for Saptahik Hindustan, Dharmayuga, Sarika, Kadambini.