A combination of static and time-resolved spectroscopic techniques has been applied to study the low-lying excited electronic states of protein-encapsulated Au nanoclusters in terms of their energy levels and relaxation mechanisms. The energy levels were determined using photoluminescence (PL) spectroscopy. The excited state dynamics were probed using time-resolved PL techniques as well as femtosecond transient absorption (TA) spectroscopy. A simple model was proposed to account for the key spectral and dynamic features observed. This study has added new insight to the optical and dynamic properties of metal nanoclusters of interest in many applications including solar energy conversion and biomedical imaging. (C) 2014 Elsevier B.V. All rights reserved.