The IWSM is organized every two years. The first IWSM 2007 was held at Auburn University, Auburn, Alabama, USA. Then, the IWSM 2009 and IWSM 2011 were held at University of Technology of Troyes, France and Stanford University, USA, respectively. The workshop covers all aspects of sequential methodologies in mathematical statistics and information theory from theoretical developments in optimal stopping, sequential analysis, change detection to different applications in mathematical finance, quality control, clinical trials, signal and image processing, among others. The goal of the workshop is to bring together the researchers and practitioners from all areas within sequential methodologies. Moreover, IWSM 2015 will celebrate the 70th birthday of Prof. Tze Leung Lai of Standford University.