He studied arts, then medicine at the Universities of Aberdeen and Edinburgh. He became a lecturer on botany in King's College, Aberdeen, then University Librarian. In 1849 He was appointed the first Professor of Natural History at Queen's College, Belfast and became a Member of the Belfast Natural History Society. In 1860 he returned to Aberdeen University as Professor of Botany. Dickie worked, most importantly on the range and depth of marine algae and on material from the Challenger expedition.