This article proposes a re-examination of the phases of construction and decoration at the shrine of ‘Abd al-Samad in Natanz and demonstrates that the core fabric and elements of architectural revetments of the shrine are datable to the Seljuq period (431-590/1040-1194), or slightly later. The structure was repurposed and redecorated, including the addition of extensive lustre tiles and stucco, for ‘Abd al-Samad by Zayn al-Din al-Mastari in the early years of the fourteenth century in a series of separate phases. Particular attention is focused on the nature of the original decoration of the shrine, revealed beneath the mortar which held the, now largely removed, Ilkhanid tilework in place. Scrutiny of the decorative interventions illustrates that the application of lustre revetments in the shrine also determined a major change of the function of the monument, from a simple burial structure into a pilgrimage centre in its own right.