Background: Bronchial asthma is one of the most common chronic pediatric diseases. It is a heterogeneous disease with multiple overlapping phenotypes. Biomarkers have been investigated for better phenotype characterization and to identify the response to targeted therapies. Purpose: The study aimed to assess serum periostin level and mean platelet volume in children with asthma flare-ups compared to age and sex-matched healthy controls. Methods: This case-control study included one hundred asthmatic children and fifty healthy children as controls. Both groups were aged 6-12 years. Bronchial asthma was diagnosed according to the Global Initiative for Asthma (1). Blood mean platelet volume and serum periostin levels were assessed for both groups. Results: The mean platelet volume was significantly lower in the patients group (9±1 fL) than in the controls (11±1 fL) (P < 0.001). Serum periostin was significantly higher in the patients group (78.85±26.33 ng/ml) than in the controls (42.72±3.4 ng/ml) (P