CaCo₂As₂, an isostructural cobalt analogue of the “122” iron arsenides, provides a useful platform for investigating the interplay among a collapsed-tetragonal lattice, itinerant Co 3d electrons, and transitionmetal-site vacancies. Although its low-temperature magnetic ground state is known to be sensitive to the Co 3d states near the Fermi level and to Co deficiency, the connection between the actual Co occupancy and the magnetic ordering temperature remains to be clarified. Here we investigate the crystal structure and low-temperature magnetic order of a self-flux-grown CaCo₂As₂ single crystal using electrical transport, magnetization, and single-crystal neutron diffraction measurements. The resistance decreases monotonically on cooling, confirming metallic transport. No pronounced resistive anomaly is observed at the magnetic transition, suggesting that the onset of long-range antiferromagnetic order only weakly affects carrier scattering in this itinerant system. Magnetic susceptibility and isothermal magnetization measured for H || ab and H || c reveal pronounced uniaxial anisotropy. In particular, the low-temperature M(H) curve for H || c exhibits a field-induced spin-flop transition, identifying the c axis as the magnetic easy axis. Single-crystal neutron diffraction at 45 K, in the paramagnetic state, confirms the ThCr₂Si₂-type collapsed-tetragonal structure, with a = b = 3.989 Å, c = 10.330 Å, and an interlayer As-As distance of 2.7577 Å. Refinement of the nuclear structure gives a Co occupancy of 88.8(1.6)%, corresponding to CaCo_1.78(3)As₂, indicating a relatively high concentration of Co vacancies. Upon cooling to 4 K, eight additional Bragg reflections, (111), (113), (115), (-111), (-113), (-115), (201), and (203), appear at positions forbidden by the body-centered nuclear structure. These reflections are magnetic in origin and can be indexed with the propagation vector k = (0, 0, 1). This magnetic propagation vector identifies an Atype antiferromagnetic structure, with ferromagnetic alignment of Co moments within each Co layer and antiferromagnetic stacking between adjacent layers. The absence of a resolvable (001) magnetic reflection further indicates that the ordered moments are oriented predominantly along the c axis. Symmetry analysis yields two candidate magnetic space groups compatible with c-axis moments. The P_I4₂/mnm model is ruled out by the observed extinction conditions, whereas the P_I4/nnc model accounts for the measured magnetic intensities and gives an ordered moment of 0.311(15)μ_B/Co at 4 K. Temperature-dependent neutron diffraction of the (111) magnetic reflection gives a Néel temperature of T_N ≈ 36 K. Compared with previous reports, the present crystal has a higher Co-vacancy concentration, a substantially lower T_N, and a similarly small ordered moment. These results indicate that Co vacancies primarily weaken the Co-Co exchange network and suppress the ordering temperature of the itinerant A-type antiferromagnetic state, rather than substantially altering the ordered moment. Our results provide microscopic evidence for the coupled roles of collapsed-tetragonal bonding, transition-metal-site vacancies, and itinerant magnetism in CaCo₂As₂.