 Mohr returned to Denmark in 1681; he had dedicated "Euclides Danicus" to Christian V and hoped for a position in exchange, but was offered only a position as a shipyard supervisor, which he declined.He married Elizabeth von der Linde of Copenhagen on 19 July 1687, and soon after returned to Holland; their son, Peter Georg Mohrenthal, eventually settled in Dresden as a bookseller and publisher.In 1695 he took a job with Tschirnhaus, and spent his last few years as a guest in Tschirnhaus's house.