Pressure provides a clean and continuous route for tuning electronic structure and magnetic interactions in itinerant ferromagnets without introducing chemical disorder. Here, we report high-pressure structural, transport, and electronic structure studies of hexagonal ferromagnetic SmCrGe${}_3$, a rare-earth chromium germanide that exhibits giant uniaxial magnetocrystalline anisotropy and strong coupling between localized Sm $4f$ and itinerant Cr $3d$ electrons. Synchrotron high-pressure x-ray diffraction measurements reveal that the hexagonal $P{6}_3/mmc$ structure remains stable up to 10 GPa without a crystallographic phase transition, indicating that the pressure-driven evolution is primarily electronic rather than structural in origin. High-pressure electrical resistance measurements show a nonmonotonic pressure dependence of the Curie temperature (T${}_C$) inferred from resistance anomaly, where T${}_C$ initially decreases with pressure, followed by a slight recovery before the magnetic order is suppressed above 6.4 GPa. Concomitantly, a low-temperature resistance minimum emerges above 4.3 GPa, consistent with enhanced Kondo-like scattering associated with Sm $4f$ electrons. Density functional theory calculations on SmCrGe${}_3$ reveal a highly pressure-sensitive Cr-derived flat band near the Fermi level. Systematic lattice-parameter tuning calculations further show that anisotropic lattice compression, particularly along the crystallographic c, strongly modifies the flat-band position relative to the Fermi level. At approximately 4.7 GPa, the calculated magnetic moment collapses to nearly zero as the flat band crosses the Fermi level, signaling a pressure-induced instability of the itinerant ferromagnetic state. These results identify SmCrGe${}_3$ as a promising platform for studying the coupled evolution of fragile itinerant ferromagnetism, pressure-sensitive flat-band electronic structure, and emergent $4f$-derived correlated scattering under pressure.