Costa garnered widespread acclaim for her portrayal of Amaia, a new mother in Alauda Ruiz de Azúa's Lullaby (2022).

[5] The eldest daughter of a family of two girls, her younger sister is Noemí Costa, also an actress and architect but currently dedicated to art direction.

After graduating, Costa worked for marketing agencies as an account executive at Mr. John Sample without set hours and later for a German company with strict ins and outs.

[14] The following year, Costa starred as Rym, a girl with breast cancer, who becomes the roommate of Lleó, portrayed by Àlex Monner,[1] in the second season of the television show Polseres vermelles,[15] winner of the International Emmy Award for Best Kids TV Series,[16] adapted by Steven Spielberg for North America as Red Band Society;[17] and in La Bien Querida's music video for her song "Arenas Movedizas".

[18] On stage, later that year, she was cast as Maria Kapravof in her first professional play, Atraco, paliza y muerte en Agbanäspach by Nao Albet and Marcel Borràs at the Teatre Nacional de Catalunya.

[20] Nuvol remarked, "It's surprising how Laia Costa's conviction as a somewhat hipster-esque femme fatale, plays her role entirely in German".

[41] Costa held the lead role in the short film No me quites as Laura, who eagerly waits at her house for her ex-boyfriend Luis to return after a two-month absence.

She co-starred alongside Christopher Abbott and Mia Wasikowska in Nicolas Pesce's psychological horror-thriller Piercing, based on the novel of the same name by Ryū Murakami;[52] it premiered at the 2018 Sundance Film Festival.

[56] Later that year, she was part of an ensemble cast in Dan Fogelman's drama film Life Itself with Sergio Peris-Mencheta and Antonio Banderas.

[58] Costa starred opposite Josh O'Connor in Harry Wootliff's critically acclaimed directorial debut Only You.

[59][60][61] She portrayed Elena, a Spanish arts council worker who falls in love with a student who is almost a decade younger, only for the relationship to founder as the couple faces infertility issues.

[62] It premiered in competition at the BFI London Film Festival, on 19 October 2018;[63] Mark Kermode called her performance "flawless".

The key lesson Costa took away was to trust her intuition and embrace projects aligned with her stage of life, finding personal satisfaction beyond external outcomes.

[73] Costa was also part of an ensemble cast in Alibi's British political thriller series The Diplomat, which premiered on 28 February 2023.

[76] Costa also starred in the revival of the Catalan romantic drama TV series titled Cites Barcelona, reprising the role of Paula after 7 years.

[77] She took on the lead role in the film adaptation of Sara Mesa's novel, Un amor, directed by Isabel Coixet,[78] playing Nat, a young woman who escapes to the town of La Escapa to rebuild her life, contending with the distrust of neighbors, the hostility of the landlord, and a disturbing sexual proposal from her neighbor Andreas.

[84] Costa also played the character of Moghedien, one of the Forsaken, in Amazon Video's adaptation of Robert Jordan's fantasy epic, The Wheel of Time.

[85] Additionally, she co-starred in the Spanish historical drama The Teacher Who Promised the Sea by Patricia Font,[86] which had its global premiere on October 27, 2023, at the 68th Valladolid International Film Festival.

[88] For six years, Costa relocated[89] from Barcelona[4][90] to Brickell, the financial district of Miami Florida,[89] with her husband[91][92] David López[93][94] because of his job[95][94] at a multinational retail company.