Disposable baby diapers undergo continuous innovation to improve absorption, comfort, and breathability. Despite short use, they incorporate advanced technologies and materials tailored to infants’ physiological needs. Their performance relies on absorbing and retaining liquids while minimizing skin irritation, achieved through a complex interaction of layers. Diaper design prioritizes absorption, impermeability, and breathability. This study analyzes five baby diaper brands available in Tunisia to assess their breathability and comfort properties based on physical and morphological parameters. Measurements include total mass, thickness, density, and microscopic observations of topsheet, high loft, and backsheet. Air and water vapor permeability tests are also conducted to assess breathability. The results indicate that the density and morphological structure of the layers directly influence their breathability. High density and compact structure, as observed for topsheet D (0.42 g/cm3), limit the circulation of air and water vapor. This topsheet has the lowest air permeability (3903 mm/s), a reduced water vapor transmission rate (RWVP%) of 78.92%, and a high evaporative thermal resistance (RET) of 4.61 m2-Pa/W, reflecting a low capacity to evacuate heat and moisture.