| Bronze-and iron-age Celtic-speakers : what don't we know, what can't we know, and what could we know? language, genetics and archaeology in the twenty-first century | Sims-Williams, Patrick | Monograph or Collective Volume | | 2012 |
| Buchedd Beuno: The Middle Welsh Life of St Beuno | | Monograph or Collective Volume | Dublin Institute of Advanced Studies | 2018 |
| Celtic civilization : continuity or coincidence? | Sims-Williams, Patrick | Article in Journal | | 2012 |
| Celtomania and celtoscepticism | Sims-Williams, Patrick | Article in Journal | | 1998 |
| Cú Chulainn in Wales : Welsh sources for Irish onomastics | Sims-Williams, Patrick | Article in Journal | | 1990 |
| Irish influence on medieval Welsh literature | Sims-Williams, Patrick | Monograph or Collective Volume | Oxford University Press | 2011 |
| Leprechauns and Luperci, Aldhelm and Augustine | Sims-Williams, Patrick | Article in Book | | 2015 |
| New approaches to Celtic place-names in Ptolemy's Geography | | Monograph or Collective Volume | Ediciones Clásicas | 2005 |
| Owain Glyndŵr's appeal to the Irish lords in 1401 and a Welsh prophecy about a lion in Ireland | Sims-Williams, Patrick | Article in Book | | 2025 |
| Some problems in deciphering the early Irish Ogam alphabet | Sims-Williams, Patrick | Article in Journal | | 1993 |
| The additional letters of the Ogam alphabet | Sims-Williams, Patrick | Article in Journal | | 1992 |
| The Celtic inscriptions of Britain : phonology and chronology, c.400-1200 | Sims-Williams, Patrick | Monograph or Collective Volume | Blackwell Publishers | 2003 |
| The development of the Indo-European voiced labiovelars in Celtic | Sims-Williams, Patrick | Article in Journal | | 1981 |
| The double system of verbal inflexion in Old Irish | Sims-Williams, Patrick | Article in Journal | | 1984 |
| The earliest Celtic ethnography | Sims-Williams, Patrick | Article in Journal | | 2017 |
| The evidence of vernacular Irish literary influence on early medieval Welsh literature | Sims-Williams, Patrick | Article in Book | | 1982 |
| The invention of Celtic nature poetry | Sims-Williams, Patrick | Article in Book | | 1996 |
| The Irish geography of Culhwch and Olwen. | Sims-Williams, Patrick | Article in Book | | 1989 |
| The location of the Celts according to Hecataeus, Herodotus, and other Greek writers | Sims-Williams, Patrick | Monograph or Collective Volume | | 2016 |
| The medieval world of Robin Flower | Sims-Williams, Patrick | Article in Book | | 1998 |
| The submission of Irish kings in fact and fiction : Henry II, Bendigeidfran, and the dating of The Four Branches of the Mabinogi | Sims-Williams, Patrick | Article in Journal | | 1991 |
| Thought, word, and deed : an Irish triad | Sims-Williams, Patrick | Article in Journal | | 1978 |