| A sermon for Good Friday by Father Michael Walsh of Sneem | O'Sullivan, Denis | Article in Journal | | 1944 |
| Cultural politics and Irish education since the 1950s : policy paradigms and power | O'Sullivan, Denis | Monograph or Collective Volume | Institute of Public Administration | 2005 |
| Irish educational policy : process and substance | | Monograph or Collective Volume | Institute of Public Administration | 1989 |
| Saint Malachy, the Gill abbey of Cork, and the rule of Arrouaise | O'Sullivan, DenisWalsh, T. J. | Article in Journal | | 1949 |
| Social commitment and adult education : essays in honour of Alfred O'Rahilly, an Irish educator | O'Sullivan, Denis | Monograph or Collective Volume | [s.n.] | 1989 |
| Some medieval houses in the barony of Imokilly, Co. Cork | O'Sullivan, Denis | Article in Journal | | 1946 |
| The Augustinian convent of medieval Cork | O'Sullivan, Denis | Article in Journal | | 1941 |
| The causes, development and relief of distress in Mayo in 1831 | O'Sullivan, Denis M. | Thesis | | 1968 |
| The Cistercian Abbey of St Mary de Castro Dei, Fermoy, Co. Cork | O'Sullivan, Denis | Article in Journal | | 1946 |
| The Cistercian abbey of St Mary de Fonte Vivo, diocese of Ross, Co. Cork | O'Sullivan, Denis | Article in Journal | | 1944 |
| The Cistercian Abbey of Tracton, Co. Cork | O'Sullivan, Denis | Article in Journal | | 1939 |
| The Cork School of Medicine : a history | O'Sullivan, Denis J. | Monograph or Collective Volume | UCC Medical Alumni Association, University College Cork | 2007 |
| The Franciscan friary of medieval Cork | O'Sullivan, Denis | Article in Journal | | 1940 |
| The ideational base of Irish educational policy | O'Sullivan, Denis | Article in Book | | 1989 |
| The monastic establishments of medieval Cork | O'Sullivan, Denis | Article in Journal | | 1943 |
| The natural history of Ireland : included in Book one of the Zoilomastix of Don Philip O'Sullivan Beare | O'Sullivan, Beare, Philip, 1590?-1660? | Monograph or Collective Volume | Cork University Press | 2009 |
| The testament of John de Wynchedon of Cork, anno 1306 | | Article in Journal | | 1956 |
| Three little-known monastic establishments of mediaeval Cork | O'Sullivan, Denis | Article in Book | | 1947 |