The pressure-temperature phase diagram (for pressures up to 23 kbar) of bis-tetramethyltetrathiofulvalene thiocyanide, (TMTTF)₂SCN, has been determined through needle axis resistivity measurements. The authors find two distinct metal-insulator (MI) transitions. At low pressures there is an MT transition at high temperature T_I(P) (near 160K at 1 bar); T_I falls with increasing pressure (dT_I/dP approximately -2K kbar^-1) and is abruptly suppressed for pressures above 15 kbar where a low-temperature (T_II approximately 15K) MI transition is stabilised. In a narrow pressure domain just below 15 kbar pronounced hysteretic behaviour is observed near T_I and effects associated with both of these MI transitions are seen. By comparison with the behaviour of other members of the isostructural families (TMTTF)₂X and (TMTSeF)₂X they associate T_I with an anion-disorder transition and T_II with a lattice distortion or spin density wave instability on the TMTTF stack. These results confirm a strong correspondence between the properties of the (TMTTF)₂X and (TMTSeF)₂X families, in particular with respect to the behaviour of those materials containing non-centrosymmetric anions.