Background: Patients with end stage renal disease on regular hemodialysis (HD) commonly present with volume overload. This has been found to be associated with increased incidence of pulmonary hypertension (PH) and chronic lung congestion. Objective: The aim of the study was to determine the effect of interdialytic weight gain (IDWG) on pulmonary artery pressure by echocardiography and lung congestion by lung ultrasound. Patients and Methods: This observational cross-sectional study was conducted on 60 patients on regular haemodialysis at Nasser Institute Hospital, Cairo. Patients were divided into 2 groups: Group (I) 30 patients with IDWG < 3.5% of their dry weight, and Group (II) 30 patients with IDWG > 3.5 % of their dry weight. Results:Patients with increased IDWG > 3.5% (group 2) had pre-HD higher pulmonary artery pressure (PAP) than those with IDWG < 3.5% (group 1) and patients with IDWG > 3.5% had more change in their PAP post HD session than those with IDWG < 3.5% but no significant difference between the change after the HD session in both groups. There is a significant relation between HD duration, anemia, and hypercalcemia with PH. Patients with more increased IDWG > 3.5 % (group 2) had higher pulmonary congestion than those with IDWG < 3.5% (group 1) and patients with IDWG < 3.5% had more change in their lung congestion level after the HD session than those with IDWG > 3.5% but no statistical significance between the change in both groups. Conclusion: Increase in IDWG% over 3.5% significantly affects lung congestion and pulmonary hypertension in dialysis patients.