Objectives: This study aimed to assess the effect of water- and land-based exercise on lung function in children with post COVID-19 condition. Methods: This was a randomized controlled trial. Children with post COVID-19 condition aged 10-12 years were randomly assigned to water-based exercise (AQUA), land-based exercise (LAND), or control group with no exercise (CONTROL). The outcomes were the changes in lung function (Lungtest Handy) from baseline to immediately after the 8-week intervention. Parameters measured included forced expiratory volume in 1 s (FEV ₁), forced vital capacity (FVC), and vital capacity (VC). Results: After the intervention, there was a significant difference (p<0.01) between the AQUA and LAND groups compared to the CONTROL group for FEV ₁ values (F (2,64) = 6.80; P = 0.91; p<0.01, η2 = 0.18), and significant differences between CONTROL and AQUA groups (p<0.01) and CONTROL and LAND groups (p<0.05) for FEV ₁ (F(2,64) = 6.96; P = 0.91; p<0.01, η2 = 0.18). Repetitions-Groups interactions for FEV ₁/%FVC (F(2,64) = 0.71, P = 0.162, p>0.05,η2 = 0.030) showed that the changes that occurred varied from group to group and the reason for this was an upward trend in LAND and AQUA and a downward trend in CONTROL. Conclusion: The study found that a supervised twice weekly 8-week exercise training program in water and on land improved lung function in children with post COVID-19 condition.