Several new medications for pulmonary arterial hypertension (PAH) have recently been introduced; however, current real-world data regarding US patients with PAH are limited. We conducted a retrospective administrative claims study to examine PAH treatment patterns and summarize healthcare utilization and costs among patients with newly diagnosed PAH treated in US clinical practice. Patients newly treated for PAH from 1 January 2010 to 31 March 2015 were followed for ≥12 months. Patient characteristics, treatment patterns, healthcare resource utilization, and costs were described. Adherence (proportion of days covered), persistence (months until therapy discontinuation/modification), and the probability of continuing the index regimen were analyzed by index regimen cohort (monotherapy versus combination therapy). Of 1637 eligible patients, 93.8% initiated treatment with monotherapy and 6.2% with combination therapy. The most common index regimen was phosphodiesterase type 5 inhibitor (PDE-5I) monotherapy (70.0% of patients). A total of 581 patients (35.5%) modified their index regimen during the study. Most patients (55.4%) who began combination therapy did so on or within six months of the index date. Endothelin receptor agonists (ERAs) and combination therapies were associated with higher adherence than PDE-5Is and monotherapies, respectively. Healthcare utilization was substantial across the study population, with costs in the combination therapy cohort more than doubling from baseline to follow-up. The majority of patients were treated with monotherapies (most often, PDE-5Is), despite combination therapies and ERAs being associated with higher medication adherence. Index regimen adjustments occurred early and in a substantial proportion of patients, suggesting that inadequate clinical response to monotherapies may not be uncommon.