Ottilia Adelborg was born in Karlskrona, Sweden.
She showed an early talent for drawing and studied at the Royal Academy of Art from 1878 to 1882. She later furthered her art education with trips to The Netherlands, Italy and France.
During her studies, she began her artistic career as an illustrator for children's magazines. She went on to become one of the first Swedish artists to make children's picture books. As a popular author and illustrator, she created more than a dozen books between 1884 and 1920, and illustrated another dozen books for other authors. Among her best-known works were Prinsarnes blomsteralfabet (The Princes' Flower Alphabet, 1892) and Pelle Snygg och barnen i Snaskeby, 1896 (translated into English as Clean Peter and the Children of Grubbylea).
She also illustrated books for adults, and designed wallpaper patterns and other home furnishings. She also was very interested in handicrafts and founded a school for lace-making in Gagnef in 1903.
Her work is held by the Ottilia Adelborg Museum, the Zorn Museum, and the National Museum in Stockholm.