INTRODUCTION: Adverse in-hospital outcomes of childhood pneumonia are well-documented, but adverse postdischarge outcomes remain unclear, especially in middle-income countries. We investigated factors associated with in-hospital and postdischarge adverse outcomes in Malaysian children with pneumonia. METHODS: Between April 2022 and April 2023, a prospective cohort of Malaysian children aged 1 month to < 12 years hospitalized with radiographic-confirmed pneumonia were enrolled and reviewed 4-6 weeks postdischarge. Composite in-hospital adverse outcomes were death, intensive care admission, or prolonged hospitalization > 5 days. Composite postdischarge adverse outcomes were chronic (> 4 weeks) wet cough, rehospitalization for acute lower respiratory infection (ALRI), or unscheduled respiratory-related doctor visit by 4-6 weeks. RESULTS: In 868 children, composite in-hospital adverse outcomes occurred in 139 (16%) (2 deaths [< 1%], 46 [5%] intensive care admissions, 136 [16%] prolonged hospitalizations). Risk factors for in-hospital adverse outcomes were: age < 6 months (adjusted odds ratio [ORadj] = 3.84, 95% confidence interval [CI] 2.13-6.93), preterm birth (ORadj = 1.81, 95% CI 1.01-3.23), partial/unvaccinated status (ORadj = 2.28, 95% CI 1.13-4.60), hypoxemia (ORadj = 4.91, 95% CI 2.95-8.20), airspace abnormalities (ORadj = 9.80, 95% CI 3.84-24.98), and anemia (ORadj = 1.70, 95% CI 1.08-2.68). Among 689/866 (80%) children reviewed postdischarge, 666 (97%) had complete data. Of these, composite postdischarge outcomes occurred in 134 (20%) children (20 [3%] chronic wet cough, 71 [11%] hospitalized ALRIs, 128 [19%] unscheduled respiratory-related doctor visits). Preterm birth (ORadj = 2.28, 95% CI 1.37-3.81) and invasive mechanical ventilation (ORadj = 2.64, 95% CI 1.16-6.00) were risk factors for postdischarge adverse outcomes. CONCLUSIONS: Children hospitalized with radiographic-confirmed pneumonia and at risk of in-hospital adverse outcomes should be monitored closely. Postdischarge follow-up is recommended for preterm children or those requiring invasive mechanical ventilation because of their risk of long-term respiratory morbidity.