Marine fisheries, as a sub-sector, may potentially play a significant role to the advancement of socio-economic development in countries that aim to spearhead the concept of ‘blue economy’ in Africa, south of the Sahara, including Tanzania. This paper assesses the contribution of marine fisheries to socio-economic development in Tanzania in terms of livelihood improvement and advancement of the national economy. Data for this paper were captured from a study that involved 1,026 respondents from eight (8) fishing villages in four coastal regions of Tanzania Mainland: Dar es Salaam, Coast, Tanga and Lindi. The study adopted a cross-sectional research design, mixed-methods research approach and triangulation of methods to ensure validity of data. Data were captured using a semi-structured questionnaire, interviews, focus group discussions and personal field observations. Obtained data were complemented with documented input from the Ministry of Livestock and Fisheries and analysed qualitatively and quantitatively. The results indicated that fishing as a primary source of income in coastal communities may contribute to household food security through the consumption of households’ catching. The results also suggested that local fishers have a limited access to resources in the exclusive economic zones (EEZs) and deep-waters due to the continued use of traditional fishing gears and vessels. It is recommended that local fishers be capacitated to exploit EEZ and deep-sea resources through support to access credit facilities and the provision of modern fishing vessels and appropriate gear. This could pave the way for the development of a fisheries sector based on EEZ and deep-sea resources.