In this work we present a new approach for the characterization of Pareto fronts for multiobjective optimal control problems. Our approach is based on the Hamilton-Jacobi-Bellman framework. We define an auxiliary optimal control for an augmented dynamical system and show that the Pareto front is a subset of the 0-level set of the corresponding augmented value function. The characterization results lead to an efficient numerical procedure for computing the entire Pareto optimal front and the corresponding optimal trajectories. Some numerical examples are considered to show the relevance of this approach.