Background/Purpose: The Development of mini-implant as a mean of maximum anchorage achieved outspread scope for enhancing better orthodontic outcomes, and their success is highly influenced by their primary stability. The aims of this study were the evaluation and comparison the primary stability of three various companies with different shapes and dimensions and to evaluate the effect of the dimensions of the miniscrew on the primary stability. Methods: The study sample of this study consisted of sixty orthodontic mini-implants (self-drilling) from three various manufactures (KJ Meditech, Hubit, and Dentos), each sort of these mini-implants was presented in two different lengths, 8 mm and 10 mm, and two different diameters, 1.4 mm and 1.6 mm. All the orthodontic mini-implants were inserted into simulated artificial bone of anterior region of the maxilla manually. Insertion torque (IT), and the pullout strength values were recorded and compared using ANOVA and Tukey honestly significant difference tests. Results: The results showed that the mean values of the pullout strength of KJ Meditech mini-implants were greater than those of Hubit and Dentos mini-implants respectively, and there was highly significant difference among these various manufactures. Furthermore, the mean values of pull out test were higher for mini-implants with dimensions 1.6 mm × 10 mm, and then followed by 1.6 mm × 8 mm, 1.4 mm × 10 mm, and 1.4 mm × 8 mm. Conclusion: The primary stability was greater in KJ Meditech mini-implants than Hubit and Dentos mini-implants respectively. Moreover, the length and the diameter had direct relation with the primary stability, and the diameter achieved higher effect on the primary stability than the length.