Indoor fungal reservoirs, particularly airborne Penicillium species, were identified throughout the ventilation system of the building and dissemination of fungi from those reservoirs was found to be occurring all the time. The objectives of this study were to determine the association between air concentration of indoor mould (Penicillium) and allergy symptoms among office workers. The study design used in this research was a cross-sectional study. Risk factors were identified through the questionnaire survey. Office workers were selected based on the proximity of their workstations to the microbiological air sampler used for the mould sampling. Results from the current study suggests that individual susceptibility of exposed subjects might be influenced by several factors associated with mould exposure; for example, inhaled mycotoxins or volatile organic compounds, which may, in some complex way, affect the immune response. This study provides the much needed preliminary baseline data for developing guidelines with validated findings that will be of use for policy decisions in Malaysia regarding indoor air quality. Results from this study are recommended for use in planning and implementing control measures in order to reduce the exposure to indoor mould and promote healthy working environment among the workers.