Background. Healthcare use for childhood illness reduces the risk of under-five deaths from common preventable diseases. However, rates of healthcare seeking for childhood diarrhea and fever remain low in most low- and middle-income countries including Ethiopia. This study aimed to assess the trends and factors for healthcare diarrhea and fever in Ethiopia from 2000 to 2016. Methods. Analysis of healthcare use for diarrhea and fever trends was done using data from four Ethiopian Demographic Health Surveys. Descriptive statistics were used to report sample characteristics and healthcare use for diarrhea and fever trends, and chi-square tests were used to assess associations between independent variables and healthcare utilization in each survey. Binary logistic regression analysis was fitted to find the factors related to healthcare utilization for diarrhea and fever. All variables with odds ratio p values <0.05 were considered as significant determinants of the outcome. Results. Healthcare seeking for diarrheal illness significantly increased from 13% (95% CI: 12.5–13.5) in 2000 to 44% (95% CI: 43.2–44.78) in 2016, while healthcare uses for fever significantly increased from 22% (95% CI: 16.7–27.3) in 2000 to 35% (95% CI: 34.3–35.7) in 2016. Factors of healthcare seeking for diarrhea in 2000–2016 were as follows: maternal age <30 years, urban residence, being a male child, nonexposure to mass media and not hearing information about oral rehydration, no desire to have more children, poor wealth index, and region. Meanwhile, factors for healthcare seeking for fever in 2000–2016 were as follows: a long distance from the nearest health facilities, first birth order, nonexposure to mass media, no desire to have more children, maternal age <30 years, urban residence, region, absence of antenatal and postnatal care utilization, poor wealth index, and being born from uneducated mothers (p values < 0.05). Conclusions. Factors associated with healthcare utilization for diarrhea and fever differed between 2000 and 2016. Though Ethiopia has achieved a significant reduction in under-five mortality, it needs to accelerate the reduction through strengthening healthcare utilization for common childhood illness to avoid deaths from preventable diseases.