BaMn9[VO4](6)(OH)(2) was synthesized by hydrothermal methods. We evaluated the crystal structure based on the two possible space groups P2(1)3 and Pa (3) over bar [a = 12.8417(2) angstrom] using single-crystal and powder X-ray diffraction techniques. The structure contains three-dimensionally linked Mn9 units of a chiral paddle-wheel type. Experimental IR and Raman spectra were analyzed in terms of fundamental vanadate and hydroxide vibrational modes. The magnetic properties were investigated, and the specific heat in applied fields was studied. The dominant magnetic interactions (Mn2+, S = 5/2) are of antiferromagnetic origin, as indicated by a Curie-Weiss fit above 175 K with Theta approximate to -200 K. Canting of the spins on the geometrically frustrated triangle segment of the structural feature is considered to account for the ferrimagnetic type of long-range order at T-C approximate to 18 K. We propose a model for the spin structure in the ordered regime. Dielectric constants were measured and indicate a magnetodielectric effect at T-C, which is assigned to spin-lattice coupling.