OBJECTIVES: Pneumonia is a significant contributor to mortality and morbidity in children aged <5 years, and it is also one of the leading causes of hospitalisation for children in this age group. This study assessed the association between climate variability, patient characteristics (i.e. age, sex, weight, parental education, socio-economic status) and length of stay (LOS) in hospital for childhood pneumonia and its economic impact on rural Bangladesh. STUDY DESIGN: An ecological study design was used. METHODS: Data on daily hospitalisation for pneumonia in children aged <5 years (including patient characteristics) and daily climate data (temperature and relative humidity) between 1st January 2012 and 31st December 2016 were obtained from the Matlab Hospital (the International Centre for Diarrhoeal Disease Research, Bangladesh) and the Bangladesh Meteorological Department, respectively. A generalised linear model with Poisson link was used to quantify the association between climate factors, patient characteristics and LOS in hospital. RESULTS: The study showed that average temperature, temperature variation and humidity variation were positively associated with the LOS in hospital for pneumonia. A 1°C rise in average temperature and temperature variation during hospital stay increased the LOS in hospital by 1% (relative risk [RR]: 1.010, 95% confidence interval [CI]: 1.001-1.018) and 9.3% (RR: 1.093, 95% CI: 1.051-1.138), respectively. A 1% increase in humidity variation increased the LOS in hospital for pneumonia by 2.2% (RR: 1.022, 95% CI: 1.004-1.039). In terms of economic impact, for every 1° C temperature variation during the period of hospital stay, there is an addition of 0.81 USD/day/patient as a result of direct costs and 1.8 USD/day/patient for total costs. Annually, this results in an additional 443 USD for direct and 985 USD for total costs. CONCLUSIONS: Climate variation appears to significantly contribute to the LOS in hospital for childhood pneumonia. These findings may help policymakers to develop effective disease management and prevention strategies.