Controlling light polarization is one of the most essential routines in modern optical technology. Since the demonstration of optical pulse shaping by spatial light modulators and its potential in controlling quantum reaction path, it paved the way to many applications as coherent control of photoionization process or as polarization shaping of Terahertz (THz) pulses. Here we evidenced efficient non-resonant and noncollinear χ (2)-type light-matter interaction in femtoseconds polarization sensitive time-resolved optical measurements. Such nonlinear optical interaction of visible light and ultra-short THz pulses leads to THz modulation of visible light polarization in bulk LiNbO 3 crystal. Theoretical simulations based on the wave propagation equation capture the physical processes underlying this nonlinear effect. Apart from the observed tunable polarization modulation of visible pulses at ultra-high frequencies, this physical phenomenon can be envisaged in THz depth-profiling of materials. Over the last decade, ultrafast Terahertz spec-troscopy has gained tremendous attention thanks to the development of high-power ultrafast laser systems [9], which allowed to generate intense single-cycle picosecond pulses of electric field at THz frequencies [5, 31]. Their relatively long optical cycle period (1 ps for 1 THz) and high electric field (from hundred of kV/cm to few MV/cm) provide a new tool for studying fundamental aspects of light-matter interactions like THz-driven ballistic charge currents in semiconductors [11,20], linear [8] and nonlinear [1] control of antiferromagnetic spin waves, THz-induced dynamics in metallic ferromagnets [27] and transparent magneto-optical media [24], or even an ultrafast switching of electric polarization in ferroelectrics [14]. Field-resolved detection of ultra-short THz pulses is well known since many years and the most common technique is based on free-space electro-optic sampling, which can be implemented in two ways: non phase-matched electro-optic sampling in crystals like ZnTe [18] or GaP [30] and phase-matched electro-optic sampling in a GaSe crystal [10,12]. The latter relies on phase-matched propagation of THz 1