Barlow is the scriptwriter, as well as lead performer, in many National Theatre of Brent productions, in particular All the World's a Globe (1987), Desmond Olivier Dingle's Compleat Life and Works of William Shakespeare (1995) and The Arts and How They Was Done (2007). In non-Theatre of Brent performances, he wrote and played in the 4-part situation comedy for radio called The Patrick and Maureen Maybe Music Experience which ran for four weeks from January 1999.

He played the part of Om in the radio adaption of Terry Pratchett's Small Gods (2006), which was adapted by Robin Brooks.

Barlow played Bob whose character was besotted with his co-star Imelda Staunton, having already overcome unrequited love for another character, called Sarah (initially mistaken as Jacinta) who delivered the sandwiches in Is it Legal? (1996-1998), and played the part of the vicar in Jam & Jerusalem. He has also written and directed his National Theatre of Brent material for television, and played the part of Max in series 2 and the 2004 special of Absolutely Fabulous.

Patrick Barlow wrote a stage adaptation, Alfred Hitchcock's The 39 Steps, which premiered in June 2005 at the West Yorkshire Playhouse. After revision, the play opened at London's Tricycle Theatre in August 2006, and after a successful run transferred to the Criterion Theatre in Piccadilly in September 2006. The play has also been performed on Broadway since early 2008, in Australia by the Melbourne Theatre Company in April 2008. and in Wellington, New Zealand, by Circa Theatre in July/August 2009.

Patrick wrote the script for The Young Visiters (sic) and had a cameo as the priest. His one-time Theatre of Brent partner Jim Broadbent co-starred with Hugh Laurie.

Most of his film work has been in small, cameo roles, for example:

• Shakespeare in Love (1998) as Will Kempe
• Notting Hill (1999) as the Savoy Concierge
• Bridget Jones's Diary (2001) as Julian
• Girl From Rio (2001) as Mr. Strothers
• Nanny McPhee (2005) as Mr. Jowls