The telecommunications ecosystem naturally is a big data warehouse, which contains a treasure trove of intelligence for those who know how to mine it. However, “big data” is not the answer to making sense of this data. Why? Because Big Data for Telecommunications (BiDaTel) is not a database problem; it is a problem of understanding the telecom data. The BiDaTel-2015 Workshop intends to facilitate the exchange of ideas among researchers in data science, computer science, electrical engineering, statistics, and other disciplines who share an interest in employing data analytics, machine learning, and data mining approaches to study telecommunication ecosystems, including wireline/wireless networks, services, applications, devices, operation and support systems, billing systems, customer relation management systems, and supply chain system etc.