Mehaffy is the author of Cities Alive: Jane Jacobs, Christopher Alexander and the Roots of the New Urban Renaissance.[2] The book explores the ideas behind the United Nations’ “New Urban Agenda” to which Mehaffy contributed as a consultant to UN-Habitat.[3] 

He is also co-author, with Nikos Salingaros, of the 2014 book Design for a Living Planet,[4] a critique of conventional architectural practice and, as they argue, its wider context of a failing technology.

He is also the lead author of A New Pattern Language: Places, Networks, Processes, a followup to the 1977 book A Pattern Language: Towns Buildings, Construction, by Christopher Alexander and associates. The new book is described as “a new collection of 80 patterns (that) emerged in part from a five-year collaboration with UN-Habitat to address new urban challenges, including rapid urbanization, slum upgrading, sustainable urbanism, (and) emerging technologies...”