Background: Insecticide treated nets (ITNs) have been identified as a key strategy in addressing malaria problem among young children and pregnant women. Their utilisation among under fives, however, have been found to be low in some areas. Objective: To identify factors affecting net utilisation (sleeping under insecticide treated net) among caregivers of under fives in Makueni District in Kenya. Design: A cross-sectional, descriptive study. Setting: Eight sub-locations in Wote division Makueni district. Subjects: Four hundred caregivers of children aged five years and below. Results: The results indicated that 88.5% of caregivers were aware of ITNs. The proportion of households with children below five years that owned mosquito net were found to be 46.2%, and only 32.0% had at least a treated net. Slightly more than half of treated nets were used by under fives (52.2%) compared to 47.8% used by children over five years including adults. The main reason cited by majority of caregivers as a hindrance to net utilisation was lack of treated nets in households (72.3%). Utilisation of ITNs by under five children was found to be positively associated with knowledge of ITNs (p=0.024), marital status (p=0.018) and occupation (p=0.043). Conclusion: Utilisation of ITNs by under fives was low despite high level of awareness among caregivers. Factors such as awareness of ITNs, marital status and occupation significantly affected ITNs utilisation. Although the government with support from other stakeholders has recently embarked on large scale distribution of nets in high risky districts, more interventions from various stakeholders are needed to increase availability and accessibility of subsidised permanently treated nets, including interventions to address non-compliance to proper utilisation of nets. There is also need for intensive education emphasising on their proper and consistent use. Scaling up proper use of ITNs along with other initiatives can contribute significantly in reducing malaria.