The high-pressure behavior of kernite [ideally Na2B4O6(OH)(2)center dot 3H(2)O, a similar to 7.02 angstrom, b similar to 9.16 angstrom, c similar to 15.68 angstrom, beta = 108.9 degrees, Sp Gr P2(1)/c, at ambient conditions], an important B-bearing raw material (with B2O3 approximate to 51 wt%) and a potential B-rich aggregate in radiation shielding materials, has been studied by single-crystal synchrotron X-ray diffraction up to 14.6 GPa. Kernite undergoes an iso-symmetric phase transition at 1.6-2.0 GPa (to kernite-II). Between 6.6-7.5 GPa, kernite undergoes a second phase transition, possibly iso-symmetric in character (to kernite-III). The crystal structure of kernite-II was solved and refined. The isothermal bulk modulus (K-V0 = beta(-1)(P0,T0), where beta(P0,T0) is the volume compressibility coefficient) of the ambient-pressure polymorph of kernite was found to be K-V0 = 29(1) GPa and a marked anisotropic compressional pattern, with K(a)(0): K(b)(0): K(c)(0)similar to 1:3:1.5., was observed. In kernite-II, the K-V0 increases to 43.3(9) GPa and the anisotropic compressional pattern increases pronouncedly. The mechanisms, at the atomic scale, which govern the structure deformation, have been described.