Vanadium was introduced in dealuminated P zeolite by impregnation with a (VOSO4)-O-IV aqueous solution at 353 K in air or argon (to prevent oxidation of V-IV), leading to VSi beta and VSi beta-Ar zeolites, respectively. The samples were characterized by spectroscopy, XRD, and N-physisorption. The oxidation state and environment of V in Sip zeolite depend on the preparation parameters (i.e., on the way the solid is recovered after impregnation and on the drying temperature). In solids recovered by centrifugation, washed with distilled water, and then dried overnight at 298 K in argon, vanadium is found as extra-lattice octahedral V-IV ions as evidenced by EPR. In contrast, in solids not washed but directly dried overnight at 353 K in air or argon, vanadium is found in both cases as lattice tetrahedral V-V ions. These ions are incorporated into vacant T sites associated with SiOH, SiO-, oxygen vacancies (OVs) or nonbridging oxygen (NBOs) defects as shown by diffuse reflectance UV-visible, V-51 MAS NMR, FT-IR, and photoluminescence. The oxidation to V-V ions is suggested to be due to an electron transfer from VO2+ to trigonal equivalent to Si+ defect sites followed by reaction of the resulting VO2+ ions with particular defects of vacant T sites. These processes occur already upon drying of V-impregnated Sip at 353 K. V-51 MAS NMR allows detection of one kind of lattice tetrahedral V ions in VSi beta and two kinds in VSi beta-Ar. The formation of different kinds of tetrahedral V species is related to the presence in vacant T sites of Sip zeolite of different types of defect sites such as trigonal equivalent to Si+ defect or SiOH and SiO-groups.