Background: Nearly half of the world’s population are at risk of being infected with malaria parasite. In Ghana, 3.5 million people get infected with the disease every year and about 20,000 children die from it annually. Haematological changes associated with malaria have been reported but may vary due to age, gender, and demographic factors. Objective: This study seeks to analyse the effect of malaria on some common haematological parameters of children (1-14 years) and adults (>14 years) patients attending St. Patrick’s Hospital, Offinso, Ghana. Methodology: A total of 2076 full blood count together with malaria test data, comprising of 1200 females and 876 males, were obtained from the laboratory department with 539 (25.96%) testing positive for malaria. Results: Majority (68.65%) of the malaria positive cases were recorded in children ≤14 years. In the 15-44 years category, females recorded significantly high cases of malaria than their male counterpart. There was a significant (p<0.0001) difference between the median haemoglobin levels of children with and without malaria. Within the adult population there was no difference between the median haemoglobin levels of malaria positive and negative adults (p > 0.05). Significant differences between all studied haematological parameters of malaria infected children and adults were identified. Out of the 370 children with malaria, 14.59% had severe anaemia compared to1.78% from their adult counterpart. The risk of developing severe anaemia was also 8.22 times as high as the risk of severe anaemia in malaria adult.Although 49.46% of children and 38.46% of adult with malaria suffer from thrombocytopenia, the risk of thrombocytopenia among children with malaria was 1.29 times as high as the risk in malaria adult. Median WBC count in children was significantly (p<0.05) higher than adult. The study also showed that 87.84%, 56.21% and 22.24% of severe anaemia, leucocytosis and thrombocytopenia respectively that occurred in children with malaria can be attributed to their age. Conclusion: Children are 2.8 (OR) times more likely to suffer from malaria infection than adults whilst equal cases of malaria occur in females and males. Policy makers and stakeholders should as a matter of urgency develops malaria intervention programs targeting children, whilst health workers should closely monitor the haemoglobin levels, platelet count and WBC of malaria children, since they suffer the worse haematological abnormalities.