The book "Systems, Software and Services Process Improvement" is a collection of revised contributions from the 25th European Conference on Systems, Software and Services Process Improvement (EuroSPI), which took place in September 2018 in Bilbao, Spain. It includes 56 carefully selected and peer-reviewed full texts that emerged from 95 submitted papers. The contributions are organized into thematic sections covering various aspects of process improvement (SPI), including agility, security assessments, management issues, assessments, and best practices. The book provides valuable insights into the implementation of SPI across different industries, including medical technology and Industry 4.0, highlighting both successful and less successful approaches to process improvement. It is aimed at professionals and researchers who are addressing the challenges and opportunities of process improvement in the software and services industry.