Joanna is a leading actress in the West End and on the international stage; as Kim in Miss Saigon (London, original Australian production, original United Kingdom and Ireland Tour and 10th Anniversary Performance), Mary Magdalene in the West End revival of Jesus Christ Superstar (London), Éponine in Les Misérables (London and Belfast Concert), Fantine in Les Misérables (London and Windsor Concert performed for HM Queen Elizabeth II and the Royal Family), Mimi in Rent (European Tour), Christmas Eve in Avenue Q (London), Sheila Franklin in Hair (London), Thanh in the world premiere of The Real Love (Los Angeles), Heidi in I Sing! (London), Ingenue June in the West End premiere of The Musical of Musicals The Musical! (London), Francesca Johnson in the international premiere of The Bridges of Madison County (Manila), Inang Bayan in Rebel (Manila), Maria in West Side Story (Manila), Maria Von Trapp in The Sound of Music (Manila), The Magic of Disney in Concert (London), Nellie Forbush in South Pacific (Manila), Blue Fairy in Pinocchio: A New Musical (Singapore), West End Women (UK Tour), Defying Gravity: The Songs of Stephen Schwartz (Sydney), Grizabella in Cats (London, UK Tour, European Tour, Middle Eastern Tour, Asian Tour and 40th Anniversary Tour), Mary Magdalene in Jesus Christ Superstar in Concert (Tokyo) and Jenna in the international premiere of Waitress (Manila).

She can be heard on the cast recordings of Miss Saigon The Complete Symphonic Recording as Kim, Jesus Christ Superstar: 1996 London Cast as Mary Magdalene, the concept cast recording of The Postman and the Poet as Beatriz Gonzalez and the soundtrack of the feature film Ang Larawan as Candida. Her debut album Joanna Ampil was recorded in Abbey Road Studios in 2007 (JAY Records), followed by Try Love in 2010 (Sony Music) and Joanna Ampil in 2014 (VIVA Records). Her latest singles  are Always Better and Memory.

She portrayed Candida in the feature film Ang Larawan (The Portrait) where she won the Metro Manila Film Festival MMFF 2017, PMPC Star Awards, Gawad Pasado, Luna, Gawad Tangi, Guillermo Award, Urduja Best Heritage Film Awards and the prestigious Gawad Urian Best Actress Awards.

She can be seen in the digital and television series "Call Me Tita" (iWant TV, ABS CBN, TFC), "Babae Sa Septic Tank 3" (iWant TV),  The Quest (BBC), Mummy Autopsy (Discovery Channel) and "Broken News" (BBC).  She portrayed Corazon in Maalaala Mo Kaya's "Kadena" (ABS-CBN, iWant TV)  wherein she won the GEMS Award for Best Actress for Television.

She performed Grizabella in the 40th Anniversary Tour of Cats (South Korea, 2020/2021) during the height of Covid-19 pandemic and at one point the only performing production in the whole world. This is chronicled in the new documentary film "The Show Must Go On" directed and produced by Sammi Cannold which premiered at Broadway’s Majestic Theatre on August 9, 2021.

In the summer of 2021, Joanna made her Chichester Festival Theatre debut in Daniel Evans' reimagined production of Rogers and Hammerstein's South Pacific as Bloody Mary.