Household mold is a major problem in communities which face natural disasters such as hurricanes or flooding, and in homes with other sources of significant water intrusion; a biomarker for exposure to indoor mold could support public health investigations. We analyzed serum from 132 children with asthma living in government-subsidized housing for six microbial volatile organic compounds (2-ethyl-1-hexanol, 2-heptanone, 2-hexanone, 3-methylfuran, 3-octanone, and geosmin) using GC-MS. Fewer than 10% of the samples for three compounds (2-ethyl-1-hexanol, 2-heptanone, and 2-hexanone were quantified below the limit of detection. Associations between mold/water damage variables and mVOCs were assessed via regression analyses, adjusting for urinary cotinine and self-reported home characteristics. Children with household mold (assessed by occupant report of visual mold, mold odor, or water damage) had 32% higher serum concentrations of 2-hexanone than those living in homes without reported mold or water damage. We investigated indoor tobacco use via urinary cotinine analysis of a “first morning void spot sample” (FMV) and found that children with higher urinary cotinine had significantly higher serum 2-ethyl-1-hexanol. We found that children in homes where residents reported tobacco smoking indoors had significantly higher serum 2-ethyl-1-hexanol compared with those without reported household smoke exposure. Tobacco smoke, indoor painting, gas stoves, and carpets were not confounders in the relationship between mVOCs and mold/water damage variables. 2-hexanone, along with an index variable which included all detectable mVOCs in our panel, are promising biomarkers of recent mold exposure that could be used in concert with other detection methods. Key Message: Our study has indicated that 2-hexanone could be used as a serum biomarker for recent exposure to indoor mold. It has significant associations with well-established proxies of indoor mold growth such as mold odor and water damage. When mass home inspections are impractical such as after a hurricane, the use of 2-hexanone or the mold index of mVOCs as a biomarker would be instrumental in assessing current disaster-related mold exposure. In addition, since mold can be hidden in walls and under carpets, a mold biomarker could still be of import if hurricane clean-up has occurred and the occupants still have possible mold-related health symptoms.