Seborrhoeic keratoses are benign epidermal neoplasms that are rarely associated with other skin lesions especially malignancies. In this study, the aim was to assess the incidence of associated lesions occurring either adjacent to or contiguous with a seborrhoeic keratosis. A retrospective case series over a 12-month period was carried out. In total, 639 consecutive histologically diagnosed seborrhoeic keratoses were identified, of which 85 (9%) were found to be associated with other lesions. Of these associated lesions, 44 (7%) were malignant, with four of these found to be arising within the seborrhoeic keratosis. These associated lesions included premalignant lesions, malignancies, melanocytic lesions and miscellaneous lesions. Men (59%) were affected more commonly than women. The average age was 74 years (range 33–98 years). Seborrhoeic keratoses associated with other lesions were found most commonly on the head and neck. The incidence of associated lesions, in particular malignancy arising within seborrhoeic keratoses may be higher than previously thought. This may be an incidental phenomenon, or seborrhoeic keratosis could represent a precursor lesion. Therefore, seborrhoeic keratoses that have undergone recent clinical change should be considered for biopsy and histological examination.