The paper examines the mechanisms that contribute to the strength of green compacts produced and tested in different thermal conditions (different homological temperatures of Sn, Zn, Cu, Ni, and Mo powders compacted and tested in normal conditions). The role of powder particle shape is demonstrated using scanning electron microscopy to analyze images of the particles and fracture patterns of the compacts. Partial plastic fracture is found only in the Sn powder sample. When plastic powders with irregular, branched particles (Cu, Ni) are compacted, the mechanism of adjusting particle surfaces to one another prevails and leads to all three mechanical components: interlocking, entangling, and seizing. When plastic powders with spherical particles are compacted, deformation of particles prevails. The ratio of the tensile strength of compacts (σb.i) determined indirectly to the tensile strength (σb) of particulate material shows a semilogarithmic dependence on the ratio of compacting pressure (P) to the yield stress (σ0.2) of the particulate material. The dependence of the ratio of σb.i to the elastic modulus on the homological temperature of compacting and testing divides into two linear dependences for spherical and nonspherical particles.