Introduction: Child health, especially childhood mortality, is one of the critical indicators of human development. No child mortality is desirable, but it is still high in Bangladesh. We aimed to assess the effect of the child's desired status of mothers on childhood morbidity and mortality of Bangladesh. Data and Method: We used the data from nationally representative cross-sectional Bangladesh Demographic and Health Survey (BDHS) 2014 and restricted the analyses to children born in the past five years preceding the survey. We estimated the undesired status (excess in boy, girl, both, and parity) by subtracting an ideal number of children from the total live birth. We measured childhood mortality (neonatal, infant, and under-five mortality), morbidity (fever, diarrhea, cough, and ARI), and nutritional problems (stunting, wasting, and underweight). Finally, we utilized the chi-square test and multilevel logistic regression analyses. Findings: The prevalence of undesired children was 20.7%, 23.2%, 4.9%, and 30.3% for boys, girls, both boys and girls, and parity, respectively. Age, education, residence, division, and household wealth index were significantly associated with undesired children. The prevalence of under-five mortality was 3.1% among desired children, almost double (5.9%) among undesired children. The likelihood of under-five mortality was 85% (AOR) to 97% (COR) higher among undesired children than the desired one. Childhood malnutrition (stunting and underweight except wasting) was also higher and significantly associated with undesired children. We also found 17% (AOR: 0.83; 95% CI: 0.72, 0.96) lower postnatal checkup for undesired children. Despite lower under-five mortality among higher socioeconomic status, the relative contribution of undesired children to under-fiver mortality was larger. Conclusion: The share of childhood mortality and malnutrition was higher among undesired children. Every child should be wanted, and no unwanted pregnancies are desirable; thereby, the government should reemphasize the proper use of family planning methods to reduce child mortality and malnutrition.