Boronic acids are widely used in materials science, pharmacology, and the synthesis of biologically active compounds In this Article, geometrical structures and relative energies of dimers of boroglycine, H2N-CH2-B(OH)(2), and its constitutional isomer H3C-NH-B(OH)(2), were computed using second-order Moller-Plesset perturbation theory and density functional theory; Dunning-Woon correlation-consistent cc-pVDZ, aug-cc-pVDZ, cc-pVTZ, and aug-cc-pVTZ basis sets were employed for the MP2 calculations, and the Pople 6-311++G(d,p) basis set was employed for a majority of the DFT calculations. Effects of an aqueous environment were incorporated into the results using PCM and COSMO-RS methodology. The lowest-energy conformer of the H2N-CH2-B(OH)(2) dimer was a six-membered ring structure (chair conformation; C-i symmetry) with two intermolecular B:N dative-bonds; it was 14.0 kcal/mol lower in energy at the MP2/aug-cc-pVDZ computational level than a conformer with the classic eight-centered ring structure (C-i symmetry) in which the boroglycine monomers are linked by a pair of H-O center dot center dot center dot H bonds. Compared to the results of MP2 calculations with correlation-consistent basis sets, DFT calculations using the PBE1PBE and TPSS functionals with the 6-311++G(d,p) basis set were significantly better at predicting relative conformational energies of the H2N-CH2-B(OH)(2) and H3C-NH-B(OH)(2) dimers than corresponding calculations using the BLYP, B3LYP, OLYP, and O3LYP functionals, particularly with respect to dative-bonded structures.