Background: Silver diamine fluoride (SDF) is a cariostatic agent used to adjunctively manage dental caries in high-risk groups. However, black staining is a frequently reported side effect following SDF application and influences the acceptability of this treatment. Aim: To evaluate the staining potential of SDF and the influence of the potassium Iodide (KI) application on the degree of black staining over time. Design: Extracted carious primary molars were collected and sorted into pairs matched by tooth type, size and location of the carious lesion (n = 35). Teeth were stratified to receive either 38% SDF, KI immediately after SDF application, or 12% SDF. Standardised timelapse photography and image processing software was used to evaluate staining over a period of 7 days. Results: Following SDF application, the onset of black staining occurred within 2 min and increased in value for up to 6 h post-application. The use of KI immediately after SDF application resulted in no noticeable staining of the carious dentine or surrounding enamel. No significant differences were evident in the staining potential between the different SDF concentrations (38% and 12%). Furthermore, root surface and cementum was found to stain darker and more readily when compared with the coronal enamel surface. Conclusion: SDF has the ability to visibly stain dental hard tissues and its staining potential may be modified by application of KI.