An evidently accomplished draughtsman, Isaac Oliver (ca.1565-1617) remains an enigmatic artist in many respects. While Nicholas Hilliard’s treatise on the art of limning provides considerable insight into his material use, techniques and self-perception, no equivalent documentary evidence survives from Oliver’s hand, and many questions regarding his training, approach and oeuvre have yet to be answered. This article presents key findings from the collaborative and technically-focussed research project Secrets of a Silent Miniaturist: Technical Analysis of Isaac Oliver’s Miniatures, undertaken by the Fitzwilliam Museum and the Hamilton Kerr Institute in Cambridge (UK). The project aims to shed light on Oliver’s artistic practice through the detailed, technical study of a representative selection of his surviving miniatures, investigated through an up-to-date, non-invasive analytical and technical lens. The article discusses the discovery of near-invisible changes to compositions implemented during the initial execution, differences in execution and later history between two versions of a portrait of Henry Frederick Prince of Wales, the first identification in a miniature of a rare mercury-based white pigment whose deterioration led to later campaigns of repainting, and the use of a hitherto unacknowledged range of pigments and media in Oliver’s landscape miniatures that raises further questions about Oliver’s connection with artistic traditions on the Continent.