Alberto Mieza is a prolific Spanish voice actor known for his extensive work dubbing anime series and films into Spanish and Catalan, as well as providing voices for numerous live-action films and television series. He is recognized for his versatility, lending his voice to a wide array of characters, from iconic heroes and villains to more nuanced supporting roles.

Details about Mieza's entry into the world of voice acting indicate a somewhat serendipitous beginning. He originally studied law, but his path changed after a chance encounter with Urquinaona Studios in Barcelona. This marked the start of a long-standing career in dubbing, during which he initially practiced with home recording equipment. He is also credited as an on-screen actor in Spanish film and television, with appearances in productions like the series El grupo and the film Nadie hablará de nosotras cuando hayamos muerto.

Mieza is perhaps best known within the anime community for a series of prominent roles he dubbed in the 1990s and 2000s. He is the Spanish voice of the character Amano Jyaku across multiple entries in the Urotsukidōji franchise, including Legend of the Overfiend, Legend of the Demon Womb, Return of the Overfiend, and Inferno Road. He also provided the voice for the ambitious Reinhard von Lohengramm in the film Legend of the Galactic Heroes: My Conquest is the Sea of Stars. His repertoire from this era includes the lead role of Yuusaku Godai in the Maison Ikkoku films, Merrill Yanagawa 'Benten' in Cyber City Oedo 808, and Mephisto in Demon City Shinjuku. Other notable anime roles include Parn in Record of Lodoss War, Lt. Lambert in Sonic Boom Squadron, Naoki Ryuo in Odin: Starlight Mutiny, and Kozo Karino in Phantom Quest Corp..

Beyond classic anime, Mieza has continued to work on high-profile projects. He voiced the villainous Ardyn Izunia in the Spanish dub of the CGI film Kingsglaive: Final Fantasy XV. His film work also includes roles in major animated features such as Muta in The Cat Returns, Tanaka in One Piece Film Gold, and a character in Studio Ghibli's The Wind Rises. He has also been involved in dubbing for live-action films, such as providing the voice for Migi in the live-action adaptation of Parasyte.

In addition to his anime work, Mieza is a regular Spanish dubbing voice for several well-known Hollywood actors. He is the customary voice for David Schwimmer, perhaps most famously dubbing his character Ross Geller in the series Friends. His usual voices also include Steve Buscemi, Paul Giamatti, John Leguizamo, and Steve Zahn. He has also provided voices for animated Hollywood films, such as Timon in The Lion King and Wheelie in the Transformers live-action film series.

Throughout his career, Mieza has collaborated frequently with a large community of other voice actors in the Spanish dubbing industry. His most frequent professional collaborators include Arturo Mercado, Juan Antonio Bernal, and Angel De Gracia. His long-standing career and the breadth of his work have made him a respected and recognizable figure in Spanish dubbing, a journey he has discussed in interviews reflecting on the evolution of the profession.