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Following on from previous experimental and theoretical work [Neville et al., Nat. Commun. 7, 11357 (2016)], we report the results of a combined electronic structure theory and quantum dynamics study of the excited state dynamics of the pyrrole dimer following excitation to its first two excited states. Employing an exciton-based analysis of the à (π3s/σ*) and B ̃ (π 3 s / 3 p / σ * ) states, we identify an excited-state electron transfer pathway involving the coupling of the à (π3s/σ*) and B ̃ (π 3 s / 3 p / σ * ) states and driven by N–H dissociation in the B ̃ (π 3 s / 3 p / σ * ) state. This electron transfer mechanism is found to be mediated by vibronic coupling of the B ̃ state, which has a mixed π3s/3p Rydberg character at the Franck-Condon point, to a high-lying charge transfer state of the πσ* character by the N–H stretch coordinate. Motivated by these results, quantum dynamics simulations of the excited-state dynamics of the pyrrole dimer are performed using the multiconfigurational time-dependent Hartree method and a newly developed model Hamiltonian. It is predicted that the newly identified electron transfer pathway will be open following excitation to both the à (π3s/σ*) and B ̃ (π 3 s / 3 p / σ * ) states and may be the dominant relaxation pathway in the latter case. [ABSTRACT FROM AUTHOR]