There are many sources of indoor air pollution in any residence, including combustion sources of tobacco smoke, cooking, engines, heating equipment, and fireplace. Indoor air quality is very important especially for the elderly who spend most of the day indoors, but there are limited studies on warrens of Bangkok, Thailand. This study evaluated volatile organic compounds (VOCs)—benzene, toluene, ethylbenzene, and xylene (BTEX)—and carbonyl compounds (CCs) in elderly residences of five warrens in an urban area in Bangkok. All active indoor and outdoor air samples during a 24-h period were applied to charcoal tubes for BTEX analyses using GC/FID and 2,4-dinitrophenylhydrazine (DNPH) cartridge for CC analyses by HPLC/UV. The median indoor VOC concentrations of benzene, toluene, ethylbenzene, xylene, formaldehyde, acetaldehyde, propionaldehyde, and valeraldehyde were 13.29, 128.51, 5.37, 16.16, 11.41, 4.81, 0.76, and 0.21 μg/m3, respectively. Total indoor VOC concentration (BTEX + CCs) of these warrens ranged from 142.32 to 272.31 μg/m3, which was higher than the outdoor VOC level. Indoor formaldehyde concentration was shown significantly higher than outdoor concentration (p < 0.01). The average lifetime cancer risks of benzene, ethylbenzene, formaldehyde, and acetaldehyde among elderly residences were 1.79E−05, 0.33E−05, 4.70E−05, and 1.02E−05, respectively, which are higher than the acceptable level. Also, hazard index (HI) was harmful to human health (HI > 1). The VOC concentrations were related to health status, specific symptoms of colds, skin irritation, and non-specific symptoms of dizziness and headache. The VOC concentrations were affected by elderly behaviors of indoor smoking (p < 0.01), mosquito repellent/insecticide spraying (p < 0.05), indoor environments of air conditioning (p < 0.001), and exhaust fan (p < 0.001). In conclusion, the elderly in urban warrens had health risk from indoor air quality, which was related to their behaviors. Good ventilation and health promotion should be recommended.