Penodwyd Martin Mansfield yn Ysgrifennydd Cyffredinol TUC Cymru ym mis Awst 2008. Mae Martin wedi chwarae rhan flaenllaw yn y strwythurau partneriaeth gymdeithasol yng Nghymru, gan gynnwys bod yn gyd-ysgrifennydd Cyngor Partneriaeth y Gweithlu gwasanaethau cyhoeddus ac arweinydd undeb llafur y Cyngor Adfywio Economaidd. Mae wedi cadeirio a chymryd rhan mewn nifer o fyrddau cynghori Llywodraeth Cymru, gan gynnwys cyflogaeth ieuenctid, caffael llywodraeth, polisi economaidd, a chyflogaeth a sgiliau.
Martin Mansfield was appointed as Wales TUC General Secretary in August 2008. Martin has played a leading role in the social partnership structures in Wales including as joint secretary of the public services Workforce Partnership Council and trade union lead on the Council for Economic Renewal.  He has chaired and participated in a number of Welsh government advisory boards including youth employment, government procurement, economic policy and employment & skills.