Crystalline α-MoO₃ belts consisting of nanosheets stacked along their [010] axes were synthesized via thermal vapor transport of MoO₃ powders at elevated temperatures. The MoO₃ belts were millimeters in length along their [001] axes and tens to hundreds of micrometers in width along their [100] axes. Mechanical and aqueous exfoliations of the belts to form two-dimensional (2D) nanosheets were processed via the scotch-tape and bovine serum albumin (BSA) assisted methods, respectively. Upon scotch-tape exfoliation, the Raman features of MoO₃ exhibited monotonic decreases in intensity as the thickness was gradually fell to approach that of a 2D nanosheet. Most Raman features eventually disappeared when a monolayer nanosheet was produced, except for the Mo–O–Mo stretching mode (Ag) at ~818 cm^-1, which was accompanied by mode-softening of up to 5 cm^-1. This mode softening, hitherto not reported for 2D α-MoO₃ nanosheets, can be attributed to lattice relaxations that are validated here via theoretical density functional perturbation theory calculations. The BSA-assisted exfoliation products exhibited a blueshift in the α-MoO₃ nanosheet absorption edge; they also revealed an absorption peak at 3.98 eV that can be attributed to their intrinsic exciton absorptions. These observations, together with the facile synthesis of high-purity α-MoO₃ crystals, illuminate the possibility of further 2D α-MoO₃ nanosheet production and lattice dynamic studies.