The OECD con­sid­ers co-production an impor­tant social inno­va­tion. This paper dis­cusses alter­na­tive def­i­n­i­tions of inno­va­tion, since tra­di­tional def­i­n­i­tions, employed by econ­o­mists for indus­try and man­u­fac­ture, do not fit well with pub­lic ser­vice pro­vi­sion. It then presents some def­i­n­i­tions of co-production, dis­cusses the rela­tion­ship between staff and their clients, and asks whether co-production is based on indi­vid­ual acts, col­lec­tive action or both. It briefly dis­cusses sev­eral fac­tors that can con­tribute to mak­ing co-production more sus­tain­able. This paper con­cludes that gov­ern­ments should develop more flex­i­ble, ser­vice spe­cific and orga­ni­za­tion spe­cific approaches for pro­mot­ing co-production, rather than look­ing for sim­ple “one size fits all” solu­tions to the chal­lenges fac­ing pub­lic ser­vice deliv­ery in the 21st Cen­tury, par­tic­u­larly for endur­ing wel­fare ser­vices. Finally, it rec­om­mends more research to pro­mote sus­tain­able co-production.