A series of boron dipyrromethene (BODIPY) dyes was tested as photosensitiser for light-driven hydrogen production in combination with the complex [Pd(PPh3)Cl2]2 as the source for catalytically active Pd nanoparticles and triethylamine as the sacrificial electron donor. In line with earlier reports, halogenated dyes showed significantly higher hydrogen production activity. All BODIPYs were fully characterised using stationary absorption and emission spectroscopy. Time-resolved spectroscopic investigations on meso-mesityl substituted compounds revealed that in non-halogenated species electron transfer from the sacrificial agent occurs to the BODIPY in a singlet excited state while in halogenated species long-lived triplet states are responsible, determining electron transfer from the sacrificial agent. Time-dependent density functional theory computations of these BODIPYs suggest the differences in the photocatalytic performance can be traced back to the varying efficiency of intersystem crossing in non-halogenated and halogenated species, not to alterations in the energy levels introduced upon substitution.