Background: Caffeine consumption is common among people throughout the world, Africarnand Ethiopia. The prevalence of the caffeine exposure during pregnancy was 69%-79% andrnexcessive caffeine consumption during pregnancy was 14%-57% in most Western countriesrnand in Ethiopia, the prevalence was 41%. The main source to caffeine is through coffee andrntea in the world and African countries, including Ethiopia. Even though there were number ofrnstudies indicating caffeine intake has reported as a risk factor for low birth weight duringrnpregnancy, the findings are not conclusive in western and no evidence in Ethiopia. Therefore,rnthis study is designed to assess the effect of maternal caffeine consumption on low birthrnweight during late pregnancy. rnObjective: The objective of this study was to determine effect of maternal caffeinernconsumption on low birth weight in Butajira Cohort, South central, Ethiopia. rnMethod: Population based Nested cohort study design was employed among 244 pregnantrnmothers from September 2018â€”May 2019 in Butajira. Beverages contain caffeine wererncollected by 24hour recall method. Birth weight was considered as outcome group. Pediatricrnweight scale was used for measurement of birth weight with in 72 hour after delivery.rnPregnant mothers exposed to caffeine consumption greater than 200mg/day was consideredrnas exposure group. The mean usual intake of caffeine was estimated by National cancerrninstitute (NCI method). Finally the effect of Caffeine on low birth weight was analyzed byrnlog binomial regression by STATA SE version 14. rnResults: The study found that 26.2% of pregnant women had daily caffeine consumptionrnmore than or equal to 200mg/day. The risk of low birth weight was four times more likely tornoccur in exposed group than in unexposed group (ARR=3.72; 95%CI: 1.76, 7.87). In otherrnhand, the risk of low birth weight was four, five and five times more likely to occur in rnmiddle, rich and richest wealth status at (ARR=4.61;95%CI (1.08,19.69,(ARR=5.39;95%CIrn(1.23,23.58),(ARR=4.54;95%CI(1.07,19.25) respectively than in poorest wealth status. rnConclusion and recommendation: In conclusion, excessive maternal caffeine consumptionrnmight results in low birth weight. Therefore, intervention that address caffeine exposurernamong pregnant mother should be designed to reduce the burden of low birth weight.