Opened in 1986, the Spiritan Missionary Seminary (SMS) is mainly for philosophy. Before 1986, Spiritan students did their studies at diocesan seminaries (Ntungamo and Kibosho) and at Kahangara with the Missionaries of Africa for one year, but then they run out of space for the increasing number of Spiritans. At the same time, the Spiritans wanted to have their own input to the formation of their students, which was not easy to do in the diocesan seminaries. The SMS started as a two year programme, but in 1995, another year was added so that students could get a BA from Urbaniana University where by then the seminary was affliated. At the moment, SMS is affliated to CUEA (Catholic University of Eastern Africa), from where the students graduate in BA in Philosophy and Social Sciences. They also get a Diploma in Philosophy and Religious studies from the Seminary.
Though Njiro is located only 6 kilometers from Arusha, on Monday, October 13, 1986, when 27 students arrived in this place, it was a deserted area surrounded by a swamp, and there were few human habitations. Furthermore, there were only two completed buildings; that is, the administration and classroom blocks. There were three staff members; namely, Fr. Pat Ryan, the Rector, Brian Cronin, the dean of studies, and Br. Paul Mbav, the bursar cum student aspiring to become a cleric. Life was so tough that staff members used to argue on theologically solid grounds, that one year at Njiro Got you often years in purgatory!
However, Njiro became more conducive to human habitation. In 1989, when Fr. Pat Ryan requested to be released of his duties as Rector, two dormitories which can accommodate 80 students had been built together with a dining hall and a chapel. Fr. Mike Begley replaced him as the Rector and in 1990, Fr. Aloysius Ndema became the Rector, until 1992 when he went for further studies. He was replaced by Fr. Brian Cronin who at first was an Acting Rector before he was confirmed Rector. He served until 1997 when Fr. Rogath Kimaryo replaced him. Meanwhile, in 1996, a staff house reminiscent of the Victorian age had been built.
Fr. Kimario was elected a General Councilor of the Spiritans in Rome in 1998. Fr. Gerard Nnamunga replaced him. More classrooms had been built and in 1999 a multipurpose hall was built. When Fr. Nnamunga was elected Provincial of the East African Province in 1999, Fr. Philip Massawe replaced him. Fr. Massawe is credited for having computerized SMS. Fr. Massawe was appointed by the Spiritan Generalate in Rome to take over as the secretary for formation and education in the whole Congregation in 2006. Fr. Eligius Mkulima replaced him until 2009 when he went for further studies. Fr. Justi Tarimo is the present Rector. The Seminary is to celebrate 25 years in 2011.