In this paper, the trans influence of boryl ligands, together with that of other ligands commonly believed to have a strong trans influence, has been investigated theoretically via density functional theory (DFT) calculations on a series of square-planar platinum (II) complexes of the form trans-[PtL (Cl)(PMe3) 2]. The following order of trans influence has been obtained:− BMe2>− SiMe3>− BH2>− SnMe3∼− BNHCH2CH2NH>− Bpin>− BOCH2CH2O>− BOCH CHO∼− Bcat∼− BCl2∼− BBr2∼− SiH3>− CH2CH3>− CH CH2>− H∼− Me>− C6H5>− SiCl3>− SnCl3>− C⋮ CH. Natural bond order analyses have been used to understand how the substituents at the boron center affect the trans-influence properties of the boryl ligands. The major factor is the σ-donor strength of the boryl ligand. However, surprisingly, very strong π acceptors also enhance the trans influence.