Maternal nutrition plays a major role in influencing fetal growth and birth outcomes. It is a modifiable risk factor which drags a significant public health consideration to avert adverse birth outcomes, specially, in low and middle income countries. Suboptimal dietary and nutritional characteristics and low birth weight are prevalent in the present study setting. This study was conducted to assess the association of maternal dietary and nutritional characteristics and newborn birth weight among pregnant mother who delivered in health institutions. Institution based cross sectional study was conducted among 541 pregnant mothers who delivered in Health Institutions of Jimma Town from March 1st, 2017 to April 30th, 2017. Data were entered into EPI data version 3.1 and analyzed using SPSS for windows, version 20.0; SPSS. Bivariate analysis was used to assess the association between birth weight and list of independent variables and to test significance of the association at p-value <0.25 for multivariable linear regression. Multivariable linear regression model was used to recognize the important predictors by controlling for possible confounding variables and statistical significance was measured at p-value <0.05. Majority of newborns had normal birth weight (91.0%). The mean birth weight of the newborns was 3224.6 ± 438.5 grams while low birth weight was 2%. In Multivariable linear regression analyses, birth weight was found to have increased by 13.5 grams (β=13.5, P=0.04), for every centimeter increment in maternal mid-upper arm circumference (MUAC). Similarly, with each increase in parity of the mother an increase in birth weight increased by 96.81 grams (β=96.81, P=0.01) was observed. Wealth index was also found to have a positive association with birth weight (β=49.04, P=0.01). Maternal MUAC, parity and wealth index were found to have a positive association with birth weight. Intervention directed on nutrition of pregnant mothers through nutrition counseling should be the major priority in addition to economic measure.