After winning numerous competitions for his singing, he moved to London in 1984 and entered the Guildhall School of Music and Drama where he studied under Rudolf Piernay.

His international operatic career began that same year when he sang the Speaker in Mozart's The Magic Flute at the Théâtre de la Monnaie in Brussels and he made his United States debut as Figaro at the Santa Fe Opera.

In 1992 Terfel made his Royal Opera House, Covent Garden debut as Masetto in Don Giovanni, with Thomas Allen in the title role.

That same year he made his Salzburg Easter Festival debut singing the role of the Spirit Messenger in Die Frau ohne Schatten.

39) and Schubert's Schwanengesang, and on 27 June he was Abimélech in Saint-Saëns's Samson and Delilah (with Plácido Domingo and Denyce Graves in the title roles), also with the CSO under Levine.

In January and February 1993, Terfel sang the role of Donner in Wagner's Das Rheingold at Lyric Opera of Chicago; Zubin Mehta conducted.

Also in 1992, he signed an exclusive recording contract with Deutsche Grammophon, and returned to the Welsh National Opera to sing Ford in Falstaff.

In 1993, he recorded the role of Wilfred Shadbolt in The Yeomen of the Guard, by Gilbert and Sullivan and sang Figaro to acclaim at the Théâtre du Châtelet in Paris.

[6] In 1994 Terfel sang Figaro at Covent Garden, and made both his Metropolitan Opera and Teatro Nacional de São Carlos debuts in the same role.

[7][8] In 2003, Terfel hosted and performed on the stage with opera tenor José Carreras and soprano Hayley Westenra in front of the capacity crowd of 10,000 people at the Faenol Festival in Wales.

[13][14] In 2010, Terfel made his debut as Hans Sachs in Wagner's Die Meistersinger in a production for Welsh National Opera, in Cardiff and on tour.

[15] On 31 July, again at the Proms, he performed in a concert from the Royal Albert Hall celebrating the works of Stephen Sondheim, in his 80th birthday year.

This production also starred Emma Thompson as Mrs Lovett, Philip Quast as Judge Turpin, and Audra McDonald as The Beggar Woman.

[19] Terfel, Thompson, and Quest reprised their roles in 2015 with the English National Opera opposite John Owen-Jones and Katie Hall as Pirelli and Johanna at the London Coliseum.

[21][22] On 6 May 2023 Terfel performed a setting in Welsh, by Paul Mealor, of Kyrie eleison at the Coronation of Charles III and Camilla in Westminster Abbey.

In 2006 the Hamburg-based Alfred Toepfer Foundation awarded Terfel its annual Shakespeare Prize in recognition of his life's work.