Water supply is the main yield-limiting abiotic factor of oil palm in Colombia. To determine the effect of water deficit on the physiology of oil palm and to assess the tolerance degree to this condition, interspecific Elaeis oleifera versus Elaeis guineensis 'U1273', 'U1859', 'U1914', and 'U1937' hybrids were planted for 60 days in soil with different water potentials (-0.042, -0.5, -1.0, and -2.0 MPa) in a complete randomized factorial design with three replications. The water potential, osmotic adjustment molecules (total and reducing sugar content), gas exchange (photosynthesis rate, stomatal conductance, water use efficiency, and leaf respiration), and vegetative growth (height, bulb diameter, leaf area, number of leaves, total dry matter, and assimilate partitioning between roots and aerial parts) were measured. Soil water potential had a significant effect on the ecophysiological response of the hybrids. At -2 MPa, there was practically no carbon dioxide assimilation. Under optimal moisture conditions, the 'U1859' hybrid recorded the highest photosynthetic rate and the lowest respiratory rate, while under moderate and severe water deficits, the 'U1937' hybrid showed the highest photosynthetic rate, the lowest respiratory rate, moved its assimilates mainly towards the roots, and was the only one to adjust its water potential (active accumulation of sugars). Two environment/genotype tolerance relationships were established based on high photosynthetic rate, low leaf respiration rate, water potential adjustment, water use efficiency under adequate moisture conditions ('U1859'>'U1937'='U1914'>'U1273'), and under water deficit ('U1937'>'U1914'>'U1859'>'U1273').