Coconut (Cocos nucifera L.) palms exhibit variation in productivity across different agro-climatic regions of India. It is important to study the factors contributing to such variation in order to increase the productivity of palms. The present study was intended to elucidate the physiological basis of yield variability in coconut across different agro-climatic regions. With this objective, seasonal variations in leaf gas exchange parameters and morphological and dry matter production characteristics of four coconut cultivars were studied at two different agro-climatic regions. Results indicated variation in gas exchange parameters of cultivars with seasons and with regions suggesting genotype-environment interactions. Overall net photosynthetic rates were higher in cultivars grown at Western ghats-hot sub humid per humid region (Kidu). Palms growing at Eastern coastal plains-hot sub humid region (Veppankulam), on the other hand, maintain greater water use efficiency. The results also indicate that, under dry conditions both stomatal and non-stomatal factors impose limitations to photosynthesis in coconut. The physiological efficiency coupled with superior morphological characters such as a larger canopy, and favourable climatic conditions for a longer period, in addition to the soil type at Veppankulam region enabled the palms to attain more of their potential productivity.