Around a third of children perceive and process their environment more deeply and are more impacted by its quality. To obtain a more comprehensive and objective measure of this Environmental Sensitivity (ES) in primary school children, we developed a semi-structured, multi-informant interview. Study 1 captures the item development while Study 2 covers the psychometric analysis and initial validation of the interview in a small pilot sample of 61 parents, their 60 children, and nine teachers, recruited from a longitudinal study involving 7–9-year-old second-graders in Swiss primary schools. Method: Interviews were conducted by trained psychologists with expertise in ES. Questionnaire data was collected from parents, children, and teachers. Findings: Parent and child interviews had good internal consistency (α = 0.83, α = 0.79, respectively) and correlated highly with each other (r = 0.535). Parent-interview correlated well with the validated sensitivity questionnaire (r = 0.514). Teacher interviews diverged from parent and child views and may inform about differences in how sensitivity is reflected across contexts. Conclusions: The new Highly Sensitive Child Interview (HSC – I) is a promising tool for a comprehensive and reliable assessment of sensitivity in primary school children and will be of value to educational psychologists following larger-scale validation. Declarations of Interest: None. •Highly sensitive children process their environment more deeply.•We present a new multi-informant interview of children's environmental sensitivity.•Parent and child interviews are characterized by good psychometric properties.•Parent and child interviews have a strong agreement between them.•The interview correlates with existing sensitivity measures.