The article is devoted to mutual help groups in Dar es Salaam, Tanzania, as an input to the country's successful nation-building process. It summarizes the results of field researches conducted by Oxana V. Ivanchenko in 2011, 2013, and 2015. The research targeted the practices of mutual help and self-organization among citizens of one of the most rapidly growing mega-cities in Africa, both its second-and third-generation old-timers and newcomers, usually the poorest Tanzanian villagers who rush to the big city in search for a better life. The methods of research include participant observation and interview, both formal and informal, with the inhabitants of uswahilini, traditional African neighborhoods, most commonly bearing the status of informal settlements. The research is focused on various forms of mutual help groups (kufa na kuzikana, mchezo/upatu, and vikoba), which nowadays tend to transform and carry out same functions of microcrediting, money-saving, loan-giving, providing the insurance in case of emergency (death, illness), and insuring socialization and strengthening of friendly relations in general. Over the course of data analysis, the authors come to a conclusion that the Tanzanians, who moved to the city, recreate the communal way of life of rural areas though in adapted forms: neighbors and colleagues become their new environment that provides social guarantees and help in difficult situation instead of relatives, and the leaders of mutual help groups help Ivanchenko and Banshchikova / Urbanization and Mutual Help Groups 35 resolve conflicts instead of the police. Strong pre-state traditions of community life and self-organization, characteristic of rural Tanzania, nowadays help urban Tanzania to grow up. And, what is even more important is that if earlier these traditions used to function only among same-tribe or same-region Tanzanians and would remain on the ethnic level, later in big cities they would flourish on inter-ethnic and supra-ethnic levels, because the need in mutual help did not disappear, while same-tribe friends and relatives were far away. Thus, it is clear that under peaceful circumstances urbanization and mutual help practices contribute to the nation-building process: people move from village to city and from traditional social bonds (on the level of tribe, region of provenance) to chosen social bonds (on nation-level, because all other ones are already overcome or non-existent).