The low-temperature microscopic magnetic properties of the quasi-2D heavy-fermion compound, CePt2In7 are investigated by using a positive muon-spin rotation and relaxation (mu+SR) technique. Clear evidence for the formation of a commensurate antiferromagnetic order below T-N approximate to 5.40 K is presented. The magnetic order parameter is shown to fit well to a modified BCS gap-energy function in a strong-coupling scenario.