Born in London, where her parents lived at the time, she was named after the River Aeron. In 1949, the family moved to the Boat House, Laugharne, Carmarthenshire, Wales. The middle child of three, she had two brothers, Llewellyn and Colm (also deceased).
At the age of 10 Aeronwy Thomas was enrolled by her mother at the Arts Educational School in Tring, Hertfordshire, now Tring Park School for the Performing Arts, also spending one year in 1958 at Dartington Hall School in Devon. Following her father's death in 1953, she and her mother went to Rome, later moving to Sicily after her mother began a relationship with her long term partner Giuseppe Fazio. Thomas earned a BA (Hons) in English and Comparative Religion at Isleworth College, and a TEFL Diploma at Woking Adult Education College. In 2003 she was awarded an Honorary Fellowship from the University of Wales, Swansea.
After learning Italian, she became a translator of Italian poetry. She was also known as an ambassador for her father's work, and as a patron of the Dylan Thomas Society. She was the President of the Alliance of Literary Societies.
A much sought-after visiting professor in schools and universities in the U.K. and abroad, in the late ‘90s she was highly popular with the students of Giuseppe Perotti School in Torino, Italy, for her distance-learning "creative writing" courses.  In 2007 she became President of IMMAGINE&POESIA (Image and Poetry), an artistic literary movement founded at Teatro Alfa, Torino, Italy.
She and her husband Trefor Ellis had two children: a son, Huw Dylan, and a daughter, Hannah.
- Later than Laugharne (Celtion, 1976)
- Christmas and Other Memories (Amwy Press, 1978)
- Poems and Memories (Pedrini, Turin)
- Christmas in the Boathouse (2003)
- Rooks and Poems (Poetry Monthly Press, 2004)
- A daughter remembers Dylan (Merton Books, 2006) - an expanded version of the booklet Christmas and Other Memories
- I Colori Delle Parole (Rotaract, 2007) - includes poems by Aeronwy Thomas and paintings by Gianpiero Actis (in Italian and English)
- Away With Words - an anthology of poetry - includes poems by Aeronwy Thomas, Beryl Myers, Anne Taylor, Frances White (Poetry Monthly Press, 2007)
- Burning Bridges (Cross-Cultural Communications, Merrick, New York, 2008)
- Shadows and Shades - Selected Poems (Poetry Monthly Press, 2009)
- My Father's Places (Constable, 2009)
- Nightwatch (17 poems) in Poet to Poet #3 (The Seventh Quarry, 2010)
- "Daughter of Dylan Thomas has died". BBC. 28 July 2009. Retrieved 28 July 2009.
- Ferris, Paul (1993). Caitlin: The Life of Caitlin Thomas. London: Pimlico. ISBN 0-7126-6290-1.
- ALS Newsletter 2007
- Ministero dell'Istruzione dell'Università e della ricerca - Ministero del Lavoro e delle Politiche sociali " Words Images Sounds. Poesia Arte Musica e le tecnologie del terzo millennio" Label Europeo 2003, Risa ed., 2004, p. 82 - 84.
- Lidia Chiarelli Immagine & Poesia - The Movement in Progress - A Cross-Cultural Communications Edition, Merrick, New York, 2013 ISBN 978-0-89304-994-2
- Aeronwy Thomas reading on poetryvlog.com on YouTube
- Wales Online obit
- TimesOnline obituary
- "This is South Wales"
- Aeronwy Thomas reading poetry on PoetCasting
- Aeronwy Thomas and her artistic-literary Movement