Objective: This study used a candidate gene approach to examine genomic variation associated with pain, anxiety, and distress in children undergoing a medical procedure. Study Design: Children aged 4-10 years having an IV catheter insertion were recruited from three Midwestern children's hospitals. Self-report measures of pain, anxiety, and distress were obtained as well as an observed measure of distress. Samples were collected from children and biological parents for analysis of genomic variation. Genotyped variants had known or suspected association with phenotypes of interest. Analyses included child-only association and family-based transmission disequilibrium tests. Results: Genotype and phenotype data were available from 828 children and 376 family trios. Children were 50% male, had a mean age of 7.2 years, and were 84% White/non-Hispanic. In family-based analysis, one single-nucleotide polymorphism (SNP; rs1143629, interleukin (IL1B) 1) was associated with observed child distress at Bonferroni-corrected levels of significance (p = .00013), while two approached significance for association with high state anxiety (rs6330 Nerve Growth Factor, Beta Subunit, [NGFB]) and high trait anxiety (rs6265 brain-derived neurotrophic factor [BDNF]). In the child-only analysis, multiple SNPs showed nominal evidence of relationships with phenotypes of interest. rs6265 BDNF and rs2941026 cholecystokinin B receptor had possible relationships with trait anxiety in child-only and family-based analyses. Conclusions: Exploring genomic variation furthers our understanding of pain, anxiety, and distress and facilitates genomic screening to identify children at high risk of procedural pain, anxiety, and distress. Combined with clinical observations and knowledge, such explorations could help guide tailoring of interventions to limit procedure-related distress and identify genes and pathways of interest for future genotype-phenotype studies.