Background <p>Fall-related injuries are the leading cause of disability and mortality among infants and toddlers. Effective prevention requires reliable assessment of fall risk, however, existing tools have several limitations. This study aimed to develop and validate a new instrument to assess risk of falls in this population.</p> Methods <p>The instrument was developed using Delphi process and validated through statistical analysis. Fourteen experts participated in the consultation, and 296 respondents completed an online cross-sectional survey. External validation was performed using a randomized controlled trial (RCT) design involving 100 participants. Evaluation measurements included Cronbach’s alpha, correlation coefficients, exploratory graph analysis, and factor analysis.</p> Results <p>The Delphi process yielded three-scale instrument, including home environment hazards (20 items), children’s activity (12 items) and parental supervision (11 items), with Cronbach’s alpha of 0.898, 0.898 and 0.907 respectively. Test–retest reliability and inter-observer reliability were 0.837 and 0.812 for home environment hazards scale. Fall-related injury hazard density (1.511 vs 1.475 per 10 m², <i>P</i> = 0.878) and dynamic hazard exposure (1.035 vs 0.847 per 10 m², <i>P</i> = 0.412) were higher in the fall-occurrence group compared to the non-fall group.</p> Conclusion <p>The newly developed instrument demonstrated high internal consistency and acceptable validity for assessing fall risk among infants and toddlers, supporting its use in the subsequent RCT study for further validation.</p> Trial registration <p>RCT study involved in our research was registered on 25 April 2021 at the Chinese Clinical Trial Registry (<a href="http://www.chictr.org.cn">http://www.chictr.org.cn</a>), clinical trial number: ChiCTR2100045859.</p>