There is increasing interest in p53 immunohistochemistry as an adjunct to haematoxylin and eosin (H&E) assessment for dysplasia in oesophageal Barrett's mucosa; however, published information on the patterns of staining remains scant. Here, we present descriptions of normal and aberrant p53 staining in non-neoplastic and dysplastic Barrett's mucosa in endoscopic mucosal resections. A retrospective series of archival endoscopic mucosal resections for biopsy proven dysplasia at our institution were retrieved for this study, comprising 28 sections from 23 patients. p53 immunohistochemistry was performed using an in-house optimised protocol and the staining pattern assessed in H&E confirmed non-neoplastic, dysplastic and neoplastic areas of Barrett's mucosa with regard to individual cell intensity and location of positive cells with respect to gland microanatomy. In non-neoplastic epithelium, normal p53 staining was weak, heterogenous and localised to the crypts. In dysplastic epithelium, p53 over-expression was seen which was of moderate to strong intensity in either a crypt predominant location or diffuse involving crypt and surface epithelium. The crypt predominant pattern was observed more commonly in low grade dysplasia while the diffuse pattern was more commonly seen in high grade dysplasia. In a minority of cases, there was complete loss of p53 staining in dysplastic epithelium and contiguous neoplasia (null phenotype). p53 immuno-expression in non-neoplastic and dysplastic Barrett's mucosa is distinctive when interpreted with regard to cell intensity and gland microanatomy. We propose that these staining patterns may assist in the interpretation of dysplasia in endoscopic biopsies of Barrett's mucosa.