A method for the introduction of trace Sn atoms into zeolite Y to impart a large mesoporous pore volume is proposed, whereby the mesoporous pore volume, framework SiO2/Al2O3 molar ratio, and crystal size were controlled by varying the Sn content. Characterization of the zeolite samples by a range of analytical techniques demonstrated that Sn entered the zeolite framework and produced superior mesopores during subsequent steam treatment, with an increased mesoporous pore volume of up to 50% being achieved compared with that of the ultrastable Y (USY) zeolite. In the catalytic cracking of 1,3,5-triisopropylbenzene, the reactivity of the Sn-containing zeolite Y differed significantly from that of USY. In addition, the Sn-containing zeolite Y exhibited a higher activity and a lower deactivation tendency than USY. Overall, the presented results indicate that this method of introducing mesopores by presetting the unstable sites in the framework of zeolite Y can have a positive influence in the preparation of mesoporous Y zeolites.