Lieber joined the Columbia University Department of Chemistry in 1987, where he was Assistant Professor (1987-1990) and Associate Professor (1990-1991) before moving to Harvard as Full Professor (1992). He holds a joint appointment at Harvard University in the Department of Chemistry and Chemical Biology and the Harvard Paulson School of Engineering and Applied Sciences, as the Joshua and Beth Friedman University Professor. He became Chair of Harvard's Department of Chemistry and Chemical Biology in 2015. Lieber was placed on "indefinite" paid administrative leave in January 2020 shortly after his arrest for making false statement to federal agents.