We present the measured spin correlation coefficient \(C_{y,y}\) for p- \(^3\) He elastic scattering at 100 MeV at the angles \(\theta _\mathrm{c.m.}=46.9^\circ \) – \(149.2^\circ \) in the center of mass system. The experiment was performed using a 100 MeV polarized proton beam in conjunction with the polarized \(^3\) He target. Proton beams were injected to the target, and scattered protons were detected by using E- \(\Delta E\) detectors which consisted of plastic and NaI(Tl) scintillators. The data are compared with rigorous numerical calculations based on realistic NN potentials as well as with the \(\Delta \) -isobar excitation . The obtained results indicate that the \(C_{y,y}\) expands the knowledge of the nuclear interactions with \(\Delta \) -isobar or those including 3NFs that are masked in nucleon-deuteron elastic scattering.