Accurate and reliable computer simulation models are alternative sources of information for replacing or enhancing information derived from costly and arduous field experiments, especially for perennial crops like oil palm. Leaf area index (LAI) is an important parameter, which is used in growth modelling of crops. Direct or destructive method of LAI measurement is time consuming, laborious and involves high cost. Hence, in the oil palm, LAI need to be measured indirectly. A computer simulation model was developed using Visual C++ to simulate leaf area index for indirect estimation of LAI Leaf area index was modelled based on OPSIM approach (Van Kraalingen, 1985). A significant relationship was found between the simulated leaf area index and measured leaf area index. A good relationship was also found between simulated LAI and Yield of the oil palm, which could be used as an indirect means of yield prediction of the oil palm. In sensitivity analysis, results showed that the simulated LAI was sensitive to both Specific Leaf Area (SLA) and extinction coefficient 'k'. From this study, it can be concluded that the LAI could be fairly estimated using the computer program developed.