Abstract Data association problems are an important component of many computer vision applications, with multi-object tracking being one of the most prominent examples. A typical approach to data association involves fifinding a graph matching or network flflow that minimizes a sum of pairwise association costs, which are often either hand-crafted or learned as linear functions of fifixed features. In this work, we demonstrate that it is possible to learn features for network-flflow-based data association via backpropagation, by expressing the optimum of a smoothed network flflow problem as a differentiable function of the pairwise association costs. We apply this approach to multi-object tracking with a network flflow formulation. Our experiments demonstrate that we are able to successfully learn all cost functions for the association problem in an end-to-end fashion, which outperform hand-crafted costs in all settings. The integration and combination of various sources of inputs becomes easy and the cost functions can be learned entirely from data, alleviating tedious hand-designing of costs