Introduction: Sacrum is a well known site for internal fixation of spine. In internal fixation, iliosacral screws applied on sacrum corpus passes through S1 vertebra pedicle. There lies epidural space, nerve root and dural sac medial to the pedicle. So, it is important to know detailed anatomy of S1 vertebra to avoid neurovascular injuries. The present study was done to provide morphometric data about dimensions of first sacral vertebra to facilitate spinal instrumentation procedures by spine surgeons. Aim: To study the morphometric characteristics of first sacral vertebra in dry human sacra. Methods: This study was conducted on 109 dry human sacra, obtained from the bone library, Department of Anatomy of a tertiary care teaching institutes. Results: Vertebral body height of first sacral vertebra at midline ranged from 19-37 mm with mean of 30.0 mm. Vertebral body maximum transverse width and vertebral body mid-diameter of first sacral vertebra were ranged from 5–61 mm (mean of 44.6 mm) and from 23–37 mm (mean of 30.3 mm) respectively. Mean posterior pedicle height of S1 vertebra on left and right side were 25.2 mm and 25 mm respectively. Mean pedicle width of S1 vertebra on left and right side were 11.3 mm and 11.5 mm respectively. Mean pedicle depth of S1 vertebra on left and right side were 31mm and 29.1mm respectively. Conclusion: Data regarding first sacral vertebra will be useful for pedicle screw fixation and also for formation of screws.