John Pickard received his BMus. degree from Bangor University in 1984, where his composition teacher was William Mathias. Between 1984 and 1985 he studied with Louis Andriessen at the Royal Conservatory in The Hague, Netherlands on a Dutch Ministry of Culture Scholarship. He was awarded a PhD in composition in 1989 and has worked at the University of Bristol since 1993. He was awarded a Personal Chair in 2009.

John is best known for his orchestral and chamber music. He has written five symphonies (No. 2 premièred by the BBC Philharmonic Orchestra in 1989; No. 3, a BBC commission for BBC National Orchestra of Wales and Mark Wigglesworth, premièred in 1997; No.5 written in 2014, once again for the BBC National Orchestra of Wales, and other orchestral works of symphonic dimensions: Sea-Change (1989), The Flight of Icarus (1990), Channel Firing (1992-93), the Trombone Concerto: The Spindle of Necessity (1997-98) and the Piano Concerto, premièred in Dresden in 2000. The Flight of Icarus (a BBC commission), received its first performance in 1991 by the BBC National Orchestra of Wales, was repeated by them at the 1996 BBC Proms and has since been played many times. In January 2006 the work received its US première by the San Francisco Symphony Orchestra and it was performed by the Cincinatti Symphony Orchestra in 2010

Other major works include the large-scale oratorio Agamemnon's Tomb (2005-08), commissioned by the Huddersfield Choral Society, and premièred by them in 2008, Tenebrae (2008-9) composed for the Norrköping Symphony Orchestra, and first performed in 2010, and the hour-long Gaia Symphony (Symphony No.4, 1991-2003) for brass band, first heard in its complete version at the 2005 Cheltenham Music Festival. John Pickard's commitment to the brass band movement was marked in 2001, when he was appointed Composer in Residence to the renowned Cory Band, a position he held until 2004. In 2005 he was commissioned to compose the test piece for the finals of the 2005 National Brass Band Championship, held at the Royal Albert Hall, London in October. This piece, Eden, has since been performed all over the world and is widely acknowledged to be one of the most important works ever written for brass band.

John Pickard's music has been praised for its large-scale architectural sense and bold handling of an extended tonal language. In a five-star review of a disc of his orchestral music (BIS CD-1578), BBC Music Magazine characterised his music as 'grounded in a much-expanded tonality that encompasses a huge and stimulating harmonic spectrum' and describing him as 'a born master of the orchestra'. Reviewing the same disc, International Record Review described it as 'music that immediately engages the attention and, above all, amply rewards repeated listening'.

John's six string quartets (1991, 1993, 1994, 1998, 2012, 2019), have received particular acclaim. Reviewing the première of the Fourth Quartet in June 1998, The Strad called it 'one of the best pieces of British chamber music to be heard for years' while the January 2003 edition of Tempo, reviewing the Sorrel Quartet's CD of Quartets 2, 3 & 4 (Dutton Epoch CDLX 71117), said 'even if Pickard were never to write another quartet in his life, his place among the greats is secure'. His 5th quartet was premièred in the Purcell Room at London's Southbank Centre in April 2013 and was described by 'Classical Source' as a work of 'hard-won affirmation' by a composer 'whose contribution to the genre has already set him among its leading practitioners'.

A disc of six chamber pieces was issued by Toccata Classics in July 2012. and a second disc of orchestral works on the BIS label (Sea-Change; Piano Concerto; Tenebrae) was issued in March 2013 and featured on the cover of the May 2013 edition of International Record Review as one of its 'outstanding' releases. Tenebrae was also shortlisted in the 2013 British Composer Awards.  2013 also saw the critically acclaimed release of a recording of John's First and Fifth Quartets (Toccata Classics). During 2014 a new recording of the Gaia Symphony was issued by BIS Records to international accliam and John's new orchestral piece Sixteen Sunrises was premiered in Japan by the Nagoya Philharmonic Orchestra in May of that year. John's Fifth Symphony was premiered by the BBC National Orchestra of Wales in June 2016 and subsequently recorded for BIS Records, together with Sixteen Sunrises and Concertante Variations. The disc was shortlisted in the Contemporary category of the Gramophone Awards in August 2018.

In 2020 BIS Records released a fifth all-Pickard disc, this time of seven works for chamber ensemble, recorded by the Nash Ensemble. The disc was named as Editor's Choice in the September 2020 Gramophone  magazine and in September 2021 won the Contemporary category of the Gramophone Classical Awards.

One of John's most recent major works, Mass in Troubled Times, to a specially written text by Gavin d'Costa, was premiered by the BBC Singers in February 2019 and nominated for an Ivor Novello Award. His orchestral piece The Art of Beginning was commissioned by the 2019 Proms as the Finale of a multi-composer project to re-imagine Elgar'a Enigma Variations. The piece was premiered at the Royal Albert Hall, London in August 2019 and broadcast on radio and television.

In addition to his compositional activities, John was General Editor of the Elgar Complete Edition between 2004 and 2016.

John Pickard's music is available through Schott Music.