In this research, the influences of the size and concentration of synthesized SAPO-34 nanozeolites on the morphological characteristics, water permeability and anti-fouling properties of PVDF/SAPO-34 ultrafiltration mixed matrix membranes were explored and compared with incorporation of commercial SAPO-34. The SAPO34 is a hydrophilic zeolite with high pore volume, which nominates itself to improve permeation properties of the PVDF membranes when incorporated into its matrix. The nature, size and shape of the synthesized SAPO-34 zeolites as well as the PVDF/SAPO-34 membrane structure were characterized by XRD, EDX and SEM techniques. Evaluation of contact angle and porosity revealed that when the SAPO-34 nanozeolites concentration in the casting solution and their crystallization time (during synthesis) augments up to 1 wt% and 18 h, respectively, the hydrophilicity and bulk porosity of PVDF membranes as well as their surface mean pore sizes enhances. As a result, the pure water flux of all membranes containing SAPO-34 nanoparticles was higher than that of the bare membrane. The lowest contact angle of 73o, the highest bulk porosity of 65%, mean pore size of 3.5 nm and pure water flux of 33 GFD belonged to the membrane which was prepared with 1 wt% of SAPO-34 with 18 h of crystallization time. FRR measurements expressed that the fouling tendency of the membranes containing synthetic SAPO-34 nanoparticles has declined compared to the bare PVDF membrane and those with commercial type. The results approved that by decreasing of the nanoparticle size, the performance of nanocomposite membranes improved.