Introduction: Dyspnea associated with pulmonary arterial hypertension (PAH) requires supplemental oxygen to maintain oxygen saturation. Many researches related to oxygen therapy in chronic obstructive pulmonary disease and cor pulmonale are available, but the effect of long-term oxygen therapy (LTOT) has not been explored in PAH patients. Aim: This study aimed to determine the effect of LTOT in patients diagnosed with PAH. Methodology: All adult patients with PAH, primary or secondary to respiratory disease who require LTOT, were included in the study. The following parameters were collected: age, gender, severity of PAH based on echocardiogram, body mass index, comorbidities, type of oxygen therapy device, amount and duration of oxygen usage, mortality, frequency of readmission, oxygenation, and vital sign parameters. Results: This was a retrospective study which included 332 participants diagnosed to have PAH after detailed echocardiogram assessment. Out of these, 32 participants were prescribed LTOT at the time of discharge. At the time of discharge, there was a significant improvement in all the vital signs and oxygenation variables. The increase in oxygenation, hemoglobin, and reduced respiratory rate after LTOT was statistically significant (P < 0.001). During follow-up after 1 year, 26 (81.3%) participants survived, 3 participants (9.4%) expired, and 3 participants (9.4%) were lost to follow-up. Conclusion: The use of oxygen therapy is beneficial in patients with PAH in terms of improvement in oxygenation and reduction in hospital readmission. Survival at 1 year is 81% in patients using LTOT.