The ornamentation of the Buddhist monasteries of Haḍḍa, administered by the Sarvāstivādin school of monks, demonstrates its fidelity to Theravāda iconography while prefiguring elements of Mahāyāna aesthetics. The purpose of this article is to examine how this decor sheds light on religious practices within these monasteries, to what degree this transformation can be ascribed to an evolution in Buddhist thought, and to a likely doctrinal shift within the Theravāda tradition at the time of the emergence of Mahāyāna speculations. The aim is also to underscore that there does not seem to have been any radical transformation in sacred art language or a sudden transition from a narrative art to an iconological decor. Quite the opposite, Haḍḍa art predominantly maintains its narrative inclination, even though it exploits an entirely different mode of representation than the better known Gandhāra schist bas-reliefs.