Purpose: The purpose of the research is to explore how to use and implement acombination of the tools value stream mapping and discrete event simulation, to supportthe decision-making in the improvement process in an organization. The researchfurther takes the sustainability aspect into consideration. Method: A deductive approach is applied in order to explore and elaborate on existingtheories to fill the identified gap in the research field. To identify already existingtheories a literature review along with a systematic literature review were conducted.Further, to enable the exploration of the purpose, a case study was performed toelaborate on the industrial implementation of the combinational tool use. Findings: The studied research field is well researched but has an identified gapregarding the combinational tool use and its industrial application. Even though, theadvantages and challenges of the integration of the tools are well elaborated on inexisting research, the methodology on how to use and implement them in anorganization was identified as inadequate and therefore this research proposes such acontribution. One of the main conclusions of the study is that integrating DES withVSM early in the process is greatly advantageous in order to utilize theircomplementary capabilities and thus achieve more decisive facts right from the start,from the so-called current state. Implications: The conclusions of the conducted research showed that there are severaladvantages with the combinational tool use but also some challenges that need to betaken into account. In order to bridge these challenges and to take them intoconsideration when implementing the tool combination, an approach was developed tosupport the decision-making within the improvement process. In this study, to enabletool integration on complex production systems, aggregation modeling was applied togenerate a reliable replica of the system. Limitations: This study contains some limitations, whereas the most influentiallimitation is related to the data collection, both in regard to time constraints and validity.Due to the limited time that the researchers had at the factory site, the data collectionperiod was limited to less than 3 months. This in turn resulted in the use of smallersample sizes. The data collected from the case company have been generalized whencreating the models, this was due to the data being too complex to fully compile andunderstand, and a “good enough” perspective was then applied. This perspective is notconsidered to affect the validity or reliability of the study in the wider sense.