Since then, its list of over 300 commissions reaches from its early support of Sir Harrison Birtwistle, Iannis Xenakis and Luciano Berio to pieces from Magnus Lindberg, Thomas Adès, George Benjamin, Steve Reich, Tansy Davies, Dai Fujikura, Jonny Greenwood, Django Bates, Roberto Carnevale, Kenneth Hesketh and Mark-Anthony Turnage.

In more recent years the ensemble has continued its commissioning relationship with a diverse range of composers including Birtwistle, Colin Matthews and Steve Reich, while giving numerous opportunities to early career composers such as Martin Suckling, Luke Bedford, Edmund Finnis and Elspeth Brooke through concert commissions and cross-art form development programmes.

In the early 2000s the ensemble's programming embraced collaborations with pop and electronica artists as it sought to connect the sound-worlds across different genres of contemporary music.

[citation needed] The London Sinfonietta has worked with a range of conductors, not least its past music directors David Atherton, Markus Stenz and Oliver Knussen.

It has had long-standing relationships with Sir Simon Rattle (in his early career), Elgar Howarth, Diego Masson, George Benjamin and Martyn Brabbins.

The Sinfonietta is a resident ensemble of the Southbank Centre, where it performs much of its London season producing events in the Royal Festival and Queen Elizabeth Halls and the Purcell Room.

The ensemble now releases recordings in partnership with different labels, which recently have included Thomas Adès' In Seven Days and Louis Andriessen's Anais Nin (on Signum), music by Pelle Gudmundsen-Holmgreen (on Da Capo) and a collaboration with Mica Levi, Chopped and Screwed (on Rough Trade).