Alternative splicing is a central tool of evolution that significantly increases the size of transcriptomes and generates functional specification. Within the human ERBB receptor gene family, only ERBB4 is known to produce functionally distinct isoforms as a result of alternative splicing. While ErbB4 signaling has been demonstrated to regulate cellular processes involved in embryogenesis, carcinogenesis and cardiovascular and psychiatric diseases, relatively little is known about the contribution of the individual isoforms in the different biological contexts. Here, we review recent findings as well as provide novel data about the distribution and functions of the ERBB4 splice variants. These observations represent an example of how minor alterations in the transcripts of a single gene can result in even antagonistic cellular responses. The observations also underline the significance of understanding the unique functions of isoforms of a potential drug target gene.