The International Workshop on Semantic Technologies in Ubiquitous, Massive and Smart Learning (STUMS) was held for the first time as part of IEEE INCoS 2014 in Salerno (Italy) on 10-12 September 2014. In the first edition, STUMS focused on Semantic Technologies and Computational Intelligence approaches enabling Ubiquitous Learning, MOOCs and Smart Learning Environments. Starting from the promising results of the 2014 edition, the main idea underlying the STUMS initiative, in 2015, is to investigate the importance of defining frameworks and technologies for supporting Seamless Learning. A Seamless Learning experience, for an individual, is characterized by the capacity to sustain the continuity of learning by connecting learning activities across locations, times, technologies, social settings and integrating different approaches to teaching, learning and assessment. The main anticipated impact of this capacity is to obtain no apparent gaps between different frames of an holisitic learning experience. Such frames can be filled, for instance, with formal, informal-intentional or accidental learning activities supported by various technologies. Hence, Smart Learning Environments, Mobile Learning, Context-aware Learning and ultimately, Ubiquitous Learning can be considered as parts which have to fit together representing the whole Seamless Learning experience. In such a scenario, STUMS 2015 aims to provide a forum to investigate approaches, frameworks and technologies which sustain continuity in Seamless Learning experiences, alignment of formal and informal activities and adaptation of both the whole experience and its parts.