A multiscale simulator for alumina film growth inside a nanoporous material during an atomic layer deposition process is developed. The model combines a continuum description at the macroscopic level of precursor gas transport inside a nanopore during exposure to each of the two precursor species (trimethyaluminum and water) with a lattice Monte Carlo simulation of the film growth on the microscopic scale. Simulation results are presented for both the Monte Carlo simulation and for the multiscale system, the latter illustrating how nonuniform deposition along the nanopore can occur when insufficient precursor exposure levels are used.