Positioning with cellular signals has increasingly gained attention in urban and indoor environments where global navigation satellite system signals have limited availability. Accurate and reliable tracking of cellular signals under complex multipath conditions remain a critical yet challenging task. This chapter mainly addresses the signal tracking and multipath mitigation issues for cellular-based positioning. Taking into account multipath channels, the cellular signal models in both time and frequency domains are derived. A general flow of baseband cellular signal processing for extracting navigation observables is described. The closed-loop tracking architecture with a low computational complexity can be used for continuously tracking the delay and carrier phase of the received cellular signal. While conventional signal tracking loops are vulnerable to multipath effects, a number of multipath mitigation techniques developed for cellular signals are illustrated in detail. Attributing to the multipath mitigation module in the signal processing flow, cellular-based positioning can be better resistant to the multipath effects and ultimately fulfil the positioning performance requirements imposed by the numerous application scenarios.