Background: Substance abuse during pregnancy is more prevalent than commonly realized.The problem is greatly underestimated in many parts of the world. Specifically limited research to date has addressed the relationship between substance use and birth outcomes among women in Ethiopia. Therefore, the study to close the gap in generating first hand information on the issue Objective: The main objective of this study was to examine the effect of maternal substance abuse on the birth weight of a newborn Methods: The study used analytic study method in the form of facility based unmatched case control study, which compares the substance use of women during pregnancy with birth weight of newborns delivered from women in Addis Ababa Hospitals using an interview with a structured and pre-tested questionnaire. Sample total sample was allocated to each health facility based on their patient load by proportionate to size, and a total of 112 cases of neonates with low birth weight were compared with 235 controls of neonates born with normal or higher birth weight to identify gaps. The data were analyzed using the SPSS-21 statistical - package. Results:- khat chewing, cigarette and shisha smoking and having a partner smoking during pregnancy were statistically significant with lower birth weight Overall, factors associated with low birth weight were mothers who had sexual violence during pregnancy, Mothers who did not attend primary school (Education) and those with history of low birth weight. Moreover, lesser weight gain during pregnancy and short birth interval were associated with low birth weight. Conclusion:- The association of low birth weight among mothers who had substance abuse was strong for particularly khat, cigarette and shisha smoking during pregnancy therefore, I recommend health professionals working in antenatal care service should be given training on counseling of mothers for banning or lowering use of substance abuse, and providing educational opportunity for girls and mothers is needed.