Infections are identified as the most common preventable cause of death in pediatric oncology patients. Assessing and stratifying risk of infections are essential to prevent infection in these patients. To date, no tool can fulfill this demand in China. This study aimed to develop a nursing work-based and Chinese-specific tool for pediatric nurses to assess risk of infection in oncology patients. This research was a modified Delphi study. Based on a literature review, a 37-item questionnaire rating on a 0–5 scale was developed. Twenty-four experts from 8 hospitals in 6 provinces of China were consulted for three rounds. Consensus for each item in the first round was defined as: the rating mean was > 3 and the coefficient of variation (CV) was < 0.5. Consensus for each item in the second round was defined as CV < 0.3. Consensus among experts was defined as: P value of Kendall's coefficient of concordance (W) < 0.05. After three rounds of consultation, a two-part tool was developed: the Immune Status Scale (ISS) and the Checklist of Risk Factors of Infection (CRFI). There were 5 items in the ISS and 14 in the CRFI. Based on the ISS score, nurses could stratify children into the low-risk and high-risk groups. For high-risk children, nurses should screen risk factors of infection every day by the CRFI, and twice weekly for low-risk children. Further study is needed to verify this tool's efficacy.