Dissertation (MA Education)This study examined the perceived influence of Tanzania Teachers Union (TTU) on improving teachers’ professional development in public secondary schools, a case of Mbozi and Momba districts (Songwe Region). The study was qualitative in nature and phenomenological design was adopted in which 30 study participants were included in the study. Of 30 study participants, 16 were TTU district executive committee members, 12 were TTU school representatives and 2 were TTU government representatives. The study participants were selected through purposive sampling techniques where the criteria were based on gender and working experiences. The study included 19 male and 11 female participants with 20 TTU officials who had been working for more than 10 years while 10 TTU officials were newly employed. The data were collected through focus group discussions, individual interviews and documentary review. The study was underpinned by the human capital theory. The data were analysed by employing thematic analysis, whereby themes and sub- themes were created based on participants' views and opinions. The study found that there was minimal support of Tanzania Teachers’ Union on the provision of on-job training; training was seldom being organized by TTU, only in the regions and districts with poor performance. In addition, the study revealed that academic seminars and workshops were being infrequently conducted and organized by TTU. The study also revealed that few union members had financially been supported by TTU in enhancing their teaching profession especially in regions with poor performance. Likewise, the study noted that teachers had different problems in subject matter, teaching techniques, and integrating ICT in the teaching and learning process. It was also revealed that the study participants perceived negatively the contribution of TTU on developing teachers‟ profession. That the union was taking much of its time on bargaining with the government on salary increments and promotions but putting less emphasis on improving teachers‟ professions. The study recommends that for TTU to have progressive professional development programmes and projects, it should establish a long and short-term strategic plan for organizing professional development activities. Likewise, the study recommends the union to establish a special unit responsible for coordinating teachers' professional development activities in public secondary schools