The interplay between the solid-state spin-crossover features and the structural properties is analyzed for the [MnIII(pyrol)3tren] complex on the basis of high-pressure and low-temperature single-crystal x-ray-diffraction experiments. In particular, the low-temperature (30 K, 105 Pa) low spin crystal structure is compared to the low-temperature (60 K, 105 Pa) high spin and to the high-pressure (293 K, 1.00 GPa) high spin crystal structures. The low-temperature structural properties show the structural modifications due to the spin crossover in a Mn(III) complex. Comparison of these structural modifications to those described for mononuclear Fe(II) spin-crossover compounds emphasizes significant differences, such as in bond length variation and polyhedron distortion, for example. Elsewhere, analysis of the high-pressure data shows that the internal stress on the metal ion is not the cause of the occurrence of the thermal spin crossover, contrary to a general belief.