Mosquito coil repellents can cause indoor air pollution accompanied by remarkable health hazards. The current study is concerned with the impacts of exposure to mosquito coil emissions related to heart histological structure of collagen, glycogen, and protein contents in male rats of two ages. In an experimental chamber, for 4 weeks, animals were allowed to inhale the mosquito coil emissions for 6 hours per day, 6 days in the week. Histological investigations using Masson trichrome stain showed extensive collagen deposition in cardiomyocytes in both exposed ages, particularly the young age. In addition, histochemical staining using periodic acid Schiff's reaction and bromophenol blue staining exhibited significant cardiac dysfunction represented by depletion in glycogen and protein contents in the exposed young and adult groups compared to the respective control groups. These findings were supported by quantitative morphometric measurements through image analysis. Consequently, exposure to mosquito coil emissions could lead to deterioration in the localization and quantification structure of heart tissue, including fibrosis.