She was born in Brighton and found fame in movies, radio and television. She appeared in several films including Beat Up the Town and All for Mary and sung on the soundtrack of The Good Companions and Doctor At Sea. In 1957, she competed in the heats of the contest to represent the United Kingdom in the 1957 Eurovision Song Contest, eventually losing out to Patricia Bredin. In the early 1960s, Day had her own comedy sketch show on BBC Television, The Jill Day Show. She also appeared on Dee Time.
Day was well known for her long slim dresses with stiff petticoat under the below-the-knee hem which she wore in numerous television appearances.
She faded from public view as public tastes for pop music changed through the late 1950s and 1960s, eventually retiring to live in London.
In 2003, an album of her most well-known songs was released, entitled The Very Best Of Jill Day.
Track List: 1. Sincerely 2. Happiness Street 3. I'm Old Fashioned 4. Holiday Affair 5. Quiet Man 6. Mangos 7. Tear Fell 8. Little Johnny Rainbow 9. I Dreamed 10. Cinco Robles 11. Give Her My Love When You Meet Her 12. I'll Think About You 13. I Hear You Knocking 14. Hold Me In Your Arms 15. Wherever You May Be 16. Far Away From Everybody 17. Snowy Snowy Mountain 18. Somewhere In The Great Beyond 19. Oh Daddy Can I Be Your Dolly Forever 20. I've Got My Love to Keep Me Warm 21. Ding Dong 22. Lonely Nightingale 23. Promises 24. Way Of Love 25. Chee Chee Oo Chee 26. Whistlin' Willie