The transition from slow to fast growth kinetics, caused by kinetic roughening, which depends on the solution supersaturation levels, has been investigated on the {101} facets of l-arginine trifluoroacetate (LATF) crystals at 296.15 K. Two different growth mechanisms (i.e., two-dimensional (2D) nucleation and continuous growth) are assumed to describe this growth transition phenomenon accurately. Experimental results indicate that the growth mode transition occurs at a critical supersaturation of σc = 1.10, and then the effective step energy barrier can be determined to be γ = 3.35 × 10−14 erg/molecule. The analysis of the experimental results for σc and γ provide the free-energy barrier at maximum (ΔG* = 7.84 × 10−14 erg/molecule) and the number of macromolecules in the critical nucleus (N* = 1.92). The energy barrier for the continuous addition of the growth units is examined to be Ec = 8.04 × 10−14 erg/molecule.