Background: Palmaris longus (PL) is a muscle with marked variations. It is harvested as a tendon graft in many surgical proceduresin which a certain length of tendon is required. The aims of the present study were to determine the variations of this tendon in Iranian population and to find whether the length of PL tendon could be estimated by measuring the forearm length and height. Methods: We examined 128 forearms of 64 cadavers. We dissected out the tendons to measure their lengths and widths. The width of the tendon was measured at its proximal end. The forearm length and height were measured from the styloid process of the ulna to the tip of the olecranon with the forearm in neutral rotation. The height of cadavers were measured from crown to the heel in supine position. Results: The palmaris longus muscles were absent bilaterally in 5 (7.8%) and unilaterally in 14 (21.8%) cadavers. The overall prevalence of the absence of PL (unilateral or bilateral) was 29.6% (24 forearms of 19 cadavers). The mean length and width of the PL were 14.2 ± 6.3 mm and 12.8 ± 7.2 mm in males and 4.00 ± 1.9 mm and 4 ± 2.1 mm in females, respectively. The mean forearms length and cadavers' height were 29 ± 1.6 cm and 172.6 ± 9.1 cm in males and 28 ± 1.2 cm and 166.5 ± 8.9 cm in females, respectively. A significant correlation was found between the length of the tendon and  forearm in both males (p <0.001) and females (p <0.001). In contrast, there was not statistically significant correlation between the forearm length and width of the tendon in either males or females (P=0.007 in males and females). Conclusions: The results of this study indicate that the length of palmaris longus tendon can be estimated based on forearm length. This estimation might be useful for surgical intervention.