The object of this study was to elucidate the seasonal patterns of energy partitioning of net radiation into sensible and latent heat fluxes and carbon dioxide (CO2) flux at a tropical deciduous forest site, i.e. a teak plantation in northern Thailand. In general, latent heat flux was more prominent than sensible heat flux in the wet (growing) season, whereas in the dry (dormant) season, sensible heat was the main form of energy emitted to the atmosphere. More specially, latent heat flux began to increase before leaf-out of teak trees and decreased 1 month earlier than leaf-fall initiation. Daytime net CO2 uptake appeared to increase with increasing amount of leaves but only at the beginning of the wet season; values peaked during the early part of wet season; and declined thereafter. This decline occurred about 3 months earlier than when latent heat flux began to decrease about 4 months earlier than the leaf-fall initiation. These results indicate that the seasonality of water and CO2 exchanges between the atmosphere and the tropical deciduous forest was substantially decoupled during the late wet season. This decoupling of the seasonality of water and carbon exchanges may be particularly important when modelling the ecohydrology of this tropical deciduous forest. Copyright © 2012 John Wiley & Sons, Ltd.