This study was to analyse the abrasive wear of differently composed diamond dentifrices loaded with 2.4 µm diamond particles on dentine and enamel surfaces in vitro. Bovine specimens were brushed with a diamond-loaded dentifrice (DD2; 2 g particles/kg), a diamond-loaded dentifrice (1.5 g/kg) containing 20% hydrated silica as extra abrasive (DD1.5+S), or a diamond-loaded dentifrice (3 g/kg) containing 20% hydrated silicaabrasive (DD3+S). Values were compared to those obtained with Colgate Total (CT) and Elmex Sensitive plus (ES). Brushing was performed using a cross brushing machine (F = 2.5 N; 120 brushing strokes/min). Abrasive wear [µm] of specimens (n = 12) was measured profilometrically and adjusted to 10,000 brushing strokes (10 kBS). Data were compared between groups using one-way ANOVA and post-hoc pairwise tests with Tukey correction, alpha = 0.05. Diamond dentifrices and ES showed no difference on dentine specimens: DD2 7.7 ± 2.6 µm/10 kBS; DD1.5+S 10.1 ± 2.3 µm/10 kBS; DD3+S 10.1 ± 2.6 µm/10 kBS; ES 7.4 ± 1.1 µm/10 kBS, while CT–brushed specimens exhibited significantly higher dentinal abrasion compared to all other groups: CT 31.0 ± 7.7 µm/10 kBS. Diamond loading significantly influenced enamel wear (mean ± SD µm/10 kBS): DD2 1.8 ± 0.5 µm/10 kBS. Conversely, addition of the silica abrasive reduced these values: DD1.5+S 1.1 ± 0.3 µm/10 kBS; DD3+S 1.6 ± 0.3 µm/10 kBS. CT and ES revealed similarly low values: CT 0.3 ± 0.1 µm/10 kBS; ES 0.2 ± 0.1 µm/10 kBS. These data suggest that abrasion caused by diamond particles in experimental toothpastes is differentially affected by diamond particle load, additional abrasives, and the type of hard tissue.