In language learning, infants are faced with the challenge of decomposing continuous speech into relevant units, such as syntactic clauses and words. Within the framework of prosodic bootstrapping, behavioral studies suggest infants approach this segmentation problem by relying on prosodic information, especially on acoustically marked intonational phrase boundaries (IPBs). In the current ERP study, we investigate processing of IPBs in 5-month-old infants by varying the acoustic cues signaling the IPB. In an experiment in which pitch variation, vowel lengthening, and pause cues are present (Experiment 1), 5-month-old German infants show an ERP obligatory response. This obligatory response signals lower level perceptual processing of acoustic cues that, however, disappear when no pause cue is present (Experiment 2). This suggests that infants are sensitive to sentence internal pause, a cue that is relevant for the processing of IPBs. Given that German adults show both the obligatory components and the closure positive shift, a particular ERP component known to reflect the perception of IPBs, independent of the presence of a pause cue, the results of the current ERP study indicate clear developmental differences in intonational phrase processing. The comparison of our neurophysiological data from German-learning infants with behavioral data from English-learning infants furthermore suggests cross-linguistic differences in intonational phrase processing during infancy. These findings are discussed in the light of differences between the German and the English intonation systems.