The Shetland ponies, which originate from harshest environments in the world islands in the north of the Atlantic Ocean, are now most popular pony breed distributed in almost every corner of the world. Reference ranges of physiological, biochemical and haematological values, which are widely used in veterinary clinics, may differ according to season, age, sex, type of feeding, and environmental circumstances of the area. Reference ranges of haematological and biochemical values of Shetland ponies are rare. The present study was therefore undertaken to evaluate the impact of season, age and sex on some haematological and biochemical values and cortisol levels in healthy ponies in Saudi Arabia. The study was conducted between December 2016 to June 2017 on ponies in and around Al-Hasa, Saudi Arabia. Twenty-three clinically healthy ponies males and females of different ages were included for haematological and biochemical analysis in this study. For each animal, blood samples were collected in summer and winter. Four physiological, fourteen haematological, sixteen biochemical parameters as well as serum cortisol levels were analysed.Heart rate, respiratory rate, pulse and rectal temperature were increased in summer in comparison to winter. Values of heart rate proved significant at P < 0.05. The results of blood haematology and biochemistry of the ponies revealed that there was no significant variation between summer and winter in most of the haematological and biochemical parameters, while there was a slight significant difference in leucocyte counts, monocytes, MCH, MPVK+, platelets and AST activity. There were significant differences in serum cortisol concentration regarding season and age but not regarding gender.