Half of the world’s population live in cities and towns where many poor urban dwellers are facing problems in gaining access to adequate supplies of nutritionally balanced food. For many urban populations, an important source of food is urban and peri-urban agriculture (UPA). A number of people in the urban centers around the world practice urban and peri-urban farming, which offers to make food available to the urban population. Unfortunately, UPA has become a controversial debate due to uncertainties of its positive verses negative effects. As UPA is gaining popularity, its environmental implications are yet to be understood and documented. If not managed well, UPA may lead to serious degradation of the environment like any other human activity. The continued reference to undocumented implications of urban agriculture causes confusion and results in difficulties in policy and decision making. As such, this paper sought to investigate UPA activities and provide empirical evaluation of the various impacts that these activities have on the environment. The results obtained indicated that the common UPA activities included crop production, livestock rearing, agro-forestry and mixed farming, with crop production having the greatest impact on the environment. The environmental effects included health risks, waste management, economic importance, health and nutrition, increase in food security, social and cultural benefits, environmental sustainability and pollution from agro-chemicals, with increase in food production having the highest impact.