Widespread cultivation of phototrophic microalgae for sustainable production of a variety of renewable products, for wastewater treatment, and for atmospheric carbon mitigation requires not only improved microorganisms but also significant improvements to process design and scaleup. The development of simulation tools capable of providing quantitative predictions for photobioreactor performance could contribute to improved reactor designs and it could also support process scaleup, as it has in the traditional petro-chemical industries. However, the complicated dependence of cell function on conditions in the microenvironment, such as light availability, temperature, nutrient concentration, and shear strain rate render simulation of photobioreactors much more difficult than chemical reactors. Although photobioreactor models with sufficient predictive ability suitable for reactor design and scaleup do not currently exist, progress towards this goal has occurred in recent years. The current status of algal photobioreactor simulations is reviewed here, with an emphasis on the integration of and interplay between sub-models describing hydrodynamics, radiation transport, and microalgal growth kinetics. Some limitations of widely used models and computational methods are identified, as well as current challenges and opportunities for the advancement of algal photobioreactor simulation.