We report the anomalous characteristics of magneto-structural phases in the vicinity of orbital/charge-ordered state (TOO/CO ∼ 220 K) below the antiferromagnetic N´eel temperature (TN ∼ 130 K) of the correlated electron system Ca0.75Sm0.25MnO3 by means of neutron diffraction, field-dependent heat-capacity, and magneto-metry studies. Our neutron diffraction study reveals an apparent coexistence of two commensurate magnetic phases with the propagation vectors kC = (1/2, 1/2, 0) and kE = (1/2, ϵ, 0) forming probably a CE phase, with ϵ ∼ 0.267(3) close to 1/4, indicating that the magnetic unit-cell coincides with the enlarged superstructure of the dimensions a × 4b × c. It was found that the moments of both magnetic phases are AFM coupled along all directions, forming an A- or a G-type ordering, where the magnetic moments of the C- and E-type phases are aligned within the ab plane and along the c axis, respectively. In the non-collinear magnetic structure C-type phase can be described with the irreducible representations of Γ6(Ax, Gy ) and Γ8(Gx, Ay ), where the Mn moments are oriented parallel to the directions [110] and [1-10]. Moreover, phenomena such as field-induced metamagnetic transitions (HT ∼ 120 kOe at 3 K), critical behavior of specific heat (CP = A|T − TN|−α), negative exchange bias effect (HEB ∼ -650 Oe at 185 K), and a zero-crossover of magnetic entropy change (-0.33≤ ∆SM ≤ 0.21) are the novel noticed in this unique composition.