Background: Cataract and glaucoma are the first and second leading causes of blindness worldwide. Although usually not severe enough to cause blindness, it is not surprising that these two diseases occur simultaneously in many patients. Many studies have demonstrated intraocular pressure reduction after cataract surgery. However, most recent data indicates that intraocular pressure (IOP) reduction after cataract surgery is more significant and sustained than previously thought. Objectives: The aim of the work is to study and measure the effect of uncomplicated phacoemulsification on intraocular pressure using air puff machine and applanation tonometer at Alazhar University Hospitals. Patients and Methods: This was a prospective randomized study carried out on 40 eyes who underwent measuring IOP by air puff and applanation tonometer before phacoemulsification and IOL implantation, and one day, one month, three months post-operatively at Al Azhar university hospitals. An informed and written consent was taken from all the patients included in this study. Results: Our study was carried out on 40 eyes who underwent measuring IOP by air puff and applanation tonometer one-day pre phaco, then underwent phacoemulsification and IOL implantation of the same IOL type, and then measuring of IOP 1 day,1 week,1 month and 3 months post-operatively. A decrease in IOP after cataract surgery has been reported. Long term studies have shown a drop in IOP of about 4 mm Hg in primary open angle glaucoma (POAG) patients, and non-glaucomatous patients. Conclusion: Cataract surgery without complication can widen the anterior chamber and lower the intraocular pressure, and can improve the visual acuity with short period of follow up, not like the traditional glaucoma surgery which needs long follow up and special care more than phacoemulsification.