 He took office when Temenggong Abu Bakar made himself a Sultan of Johor and formulated a new constitution and administrative framework for Johor in 1885.During his term as Chief Minister, Jaafar was tasked to carry out state administration for the Sultan of Johor, when the Sultan went overseas.His residence for most of the latter part of his life was Istana Bukit Senyum which was built in 1883 and a high school behind the palace, Sekolah Dato Jaafar is named after him.