This paper examines the contribution of colonial rule to food insecurity among Turkana pastoralists living in the Turkana District in the arid zone of north-western Kenya. It is argued that food insecurity in Turkana began during the colonial period. For instance, during that period, the aim was to pacify Turkana pastoralists and to ensure peace and order. This tendency had several implications. It tended to present the Turkana people as an unreliable people prone to violence and, hence, to propagate depastoralisation. Of particular importance were negative colonial policies in relation to land. The policy emphasized on drawing of political boundaries and creation of block grazing schemes. Borders were fixed, and access to key resources were curtailed with little regard to seasonal variation and the needs of the people for pasture. The policy also placed the integral Turkana tribal land area under more than one political entity, which conflicted with indigenous resource use strategies. This meant that within the new fixed tribal boundaries, the environment was placed under more severe pressure. These measures greatly affected the transhumant patterns already mastered by the Turkana pastoralists from their long experience with ecological hardships. The border restriction also destroyed the lubricating social rubric traditionally obtained through trade and intermarriages with the neighbouring tribes. Levels of conflicts over available resources increased hence affected the resilience of pastoral systems, thus rendering pastoralists more vulnerable to environmental hazards such as drought.