Over 10% of children with Wilms tumor (WT) have an underlying cancer predisposition syndrome (CPS). Cognizant of increasing demand for genetic evaluation and limited resources across health care settings, there is an urgent need to rationalize genetic referrals for this population. The McGill Interactive Pediatric OncoGenetic Guidelines study, a Canadian multi‐institutional initiative, aims to develop an eHealth tool to assist physicians in identifying children at elevated risk of having a CPS. As part of this project, a decisional algorithm specific to WT consisting of five tumor‐specific criteria (age <2 years, bilaterality/multifocality, stromal‐predominant histology, nephrogenic rests, and overgrowth features) and universal criteria including features of family history suspicious for CPS and congenital anomalies, was developed. Application of the algorithm generates a binary recommendation—for or against genetic referral for CPS evaluation. To evaluate the algorithm's sensitivity for CPS identification, we retrospectively applied the tool in consecutive pediatric patients (n = 180) with WT, diagnosed and/or treated at The Hospital for Sick Children (1997–2016). Odds ratios were calculated to evaluate the strengths of associations between each criterion and specific CPS subtypes. Application of the algorithm identified 100% of children with WT and a confirmed CPS (n = 27). Age <2 years, bilaterality/multifocality, and congenital anomalies were strongly associated with pathogenic variants in WT1. Presence of >1 overgrowth feature was strongly associated with Beckwith‐Wiedemann syndrome. Stromal‐predominant histology did not contribute to CPS identification. We recommend the incorporation of the WT algorithm in the routine assessment of children with WT to facilitate prioritization of genetic referrals in a sustainable manner. What's new? Over 10% of children with Wilms tumor (WT) have an underlying cancer predisposition syndrome (CPS). CPS recognition can lead to immediate changes in first line cancer therapy, implementation of surveillance strategies, and genetic counselling of family members. Here, as part of the MIPOGG (McGill Interactive Pediatric OncoGenetic Guidelines) study, the authors report the effectiveness of a novel, easy‐to‐use eHealth decision‐support tool in identifying those patients diagnosed with WT who are at highest likelihood of having an underlying CPS. These findings provide a systematic approach for pediatric oncologists worldwide to rationalize genetic referral practices and genetic testing for children with Wilms tumor.