Hilda Caselli was born and raised at Gammelsbo in Ramsberg in Västmanland, were her father was employed as the manager of an estate.
Her father became blind in 1859, and the family moved to Uppsala, were her brothers studied at the university: similar to many females of her generation, she and her sisters were in contrast educated in very little more than to manage a household at home.
As an adult, she educated herself in the governess training course at the newly founded pioneer female seminary of Jane Miller Thengberg in Uppsala, the Klosterskolan, and made a study trip to England in 1862.
Caselli had been inspired to this after having participated in meetings discussing the need of reform for girls' education arranged by the Tidskrift för hemmet in 1875.
In 1877, a board was created including Caselli, Therese Gyldén, Sofi Almqvist and Ellen Key, and in 1879, she arranged the first nationwide Flickskolemöte.