The Bernal (ABA)-stacked graphene trilayer is presumed to be thermodynamically more stable than the rhombohedral (ABC) counterpart. However, the thermal transformation from ABC to ABA domains does not occur at a temperature lower than 1,000 °C. Here we report that ABC-stacked trilayers are transformed to ABA-stacked layers after an organic molecule triazine is evaporated onto graphene surfaces at 150 °C. The transformation is found to always initiate at the ABA-ABC domain boundaries. Simulations based on density function theory considering the van der Waals interaction suggest that after triazine decoration the energy difference between ABA and ABC domains is larger, providing a driving force for stacking transformation. The molecular dynamics simulation results further suggest that the triazine decoration on the wrinkles at the ABC-ABA domain boundary activates the wrinkle sliding toward the ABC domains, leading to the stacking transformation from ABC to ABA.