Abstract Nanotechnology provides a wide variety of methods to resolve industrial issues, which could not be addressed previously using customary methods. It helps enable researchers to alter properties of bulk materials at the nanometer scale. Various nanomaterials have been successfully applied in many areas of petroleum engineering, particularly in drilling fluids, lost circulation, enhanced oil recovery (EOR), and cementing. This study examines the mechanical and microstructural properties of oil well cement with nanozeolite. During this research, API Class G cement was used with various concentrations of nanozeolite. Compressive strength development of Class G cement, with and without nanozeolite, was studied using an ultrasonic cement analyzer (UCA) for 24 hours under high-pressure and high-temperature (HP/HT) conditions. The porosity and permeability of set Class G cement admixed with nanozeolite was also analyzed in an automated permeameter/porosimeter after 24 hours of curing. Microstructural examination of cement samples was performed using scanning electron microscopy (SEM). Three important parameters during well cementing operations included time to achieve 50- and 500-psi compressive strength and time to achieve 2,000-psi compressive strength. These parameters were significantly altered by adding a small percentage of nanozeolite to the neat Class G cement. The addition of nanozeolite resulted in a decrease in transition time and accelerated achievement of 2,000-psi strength. Furthermore, the porosity and permeability of the set Class G cement specimens with nanozeolite decreased substantially, thus indicating a dense microstructure of the matrix. This was confirmed by microstructural investigations using SEM. Nanozeolite is nonhazardous, nontoxic and is compatible with API Class G cement. Nanozeolite can be an effective oil well cement additive because it enhances early strength, and the final compressive strength helps improve cement durability. The accelerated compressive strength development can help decrease wait-on-cement (WOC) time, thus lowering operation costs. Additionally, denser microstructure can help restrain the invasion of corrosive formation fluids.