X-ray powder diffraction (XRD), magnetic susceptibility $\ensuremath{\chi}$, isothermal magnetization $M$, heat capacity ${C}_{\mathrm{p}}$, and in-plane electrical resistivity $\ensuremath{\rho}$ measurements as a function of temperature $T$ and magnetic field $H$ are presented for ${\mathrm{CaCo}}_{1.86}{\mathrm{As}}_{2}$ single crystals. The electronic structure is probed by angle-resolved photoemission spectroscopy (ARPES) measurements of ${\mathrm{CaCo}}_{1.86}{\mathrm{As}}_{2}$ and by full-potential linearized augmented-plane-wave calculations for the supercell ${\mathrm{Ca}}_{8}{\mathrm{Co}}_{15}{\mathrm{As}}_{16}$ (${\mathrm{CaCo}}_{1.88}{\mathrm{As}}_{2}$). Our XRD crystal structure refinement is consistent with the previous combined refinement of x-ray and neutron powder diffraction data showing a collapsed-tetragonal ${\mathrm{ThCr}}_{2}{\mathrm{Si}}_{2}$-type structure with 7(1)% vacancies on the Co sites corresponding to the composition ${\mathrm{CaCo}}_{1.86}{\mathrm{As}}_{2}$ [D. G. Quirinale et al., Phys. Rev. B 88, 174420 (2013)]. The anisotropic $\ensuremath{\chi}(T)$ data are consistent with the magnetic neutron diffraction data of Quirianale et al. that demonstrate the presence of A-type collinear antiferromagnetic order below the N\'eel temperature ${T}_{\mathrm{N}}=52$(1) K with the easy axis being the tetragonal $c$ axis. However, no clear evidence from the $\ensuremath{\rho}(T)$ and ${C}_{\mathrm{p}}(T)$ data for a magnetic transition at ${T}_{\mathrm{N}}$ is observed. A metallic ground state is demonstrated from the band calculations and the $\ensuremath{\rho}(T)$, ${C}_{\mathrm{p}}(T)$, and ARPES data, and spin-polarized calculations indicate a competition between the A-type AFM and FM ground states. The ${C}_{\mathrm{p}}(T)$ data exhibit a large Sommerfield electronic coefficient reflecting a large density of states at the Fermi energy $\mathcal{D}({E}_{\mathrm{F}})$ that is enhanced compared with the band structure calculation where the bare $\mathcal{D}({E}_{\mathrm{F}})$ arises from Co $3d$ bands. At 1.8 K, the $M(H)$ data for $H\ensuremath{\parallel}c$ exhibit a well-defined first-order spin-flop transition at an applied field of 3.5 T. The small ordered moment of $\ensuremath{\approx}$$0.3{\ensuremath{\mu}}_{\mathrm{B}}$/Co obtained from the $M(H)$ data at low $T$, the large exchange enhancement of $\ensuremath{\chi}$ and the lack of a self-consistent interpretation of the $\ensuremath{\chi}(T)$ and $M(H,T)$ data in terms of a local moment Heisenberg model together indicate that the magnetism of ${\mathrm{CaCo}}_{1.86}{\mathrm{As}}_{2}$ is itinerant.