Wennberg joined Caltech in 1998. He was an associate professor of atmospheric chemistry and environmental engineering science from 1998 to 2001, becoming a full professor in 2001. In 2004, he was appointed as the R. Stanton Avery Professor of Atmospheric Chemistry and Environmental Science and Engineering.  Wennberg has been associated with the Ronald and Maxine Linde Center for Global Environmental Science at Caltech since it was established in 2008. He served as the director from 2008 to 2011, acting director from 2012 to 2014 and director from 2014 onwards.