To investigate the prevalence and prognostic impact of pulmonary hypertension (PH) in lung cancer (LC) and assess its association with long-term mortality and major adverse cardiac and cerebrovascular events (MACCE). A total of 500,530 participants enrolled in the UK Biobank between 2006 and 2010 were prospectively followed through October 31, 2022. Incident LC cases were identified during follow-up. Overall survival (OS) and MACCE were assessed according to PH status. Time-dependent Cox regression models were used to estimate adjusted hazard ratios (HRs) after controlling for demographic characteristics, smoking status, comorbidities, and histological subtype. During a median follow-up exceeding 12 years, 6,095 participants developed LC. PH was significantly more prevalent among participants with LC than among those without LC. Among patients with LC, PH was associated with significantly increased risks of mortality and MACCE. After multivariable adjustment, PH remained independently associated with adverse outcomes, with progressively greater prognostic impact over time. At 10 years, adjusted HRs were 2.88 for OS and 3.45 for MACCE. PH is an important adverse cardiopulmonary comorbidity in LC and is independently associated with worse long-term survival and cardiovascular outcomes. These findings support the potential value of early recognition and longitudinal cardiopulmonary surveillance for risk stratification and management in patients with LC.