Aim: This scoping review aimed to explore nursing students experience as simulation observers and their level of engagement in learning through use of clinical decision-making models and learning scaffolds. Background: A gap continues to exist between the published empirical literature, the role and experiences of the simulation observer and teaching scaffolds that enhance learning outcomes, despite the increased understanding of simulation and its role in preparing nursing students for practice. Further, little is known about the nursing student's experience of clinical reasoning whilst observing simulation and the impact of scaffolding observations using clinical decision-making models. Design: This scoping review was conducted using the methodological framework of Arksey and O'Malley (2005) and the PRISMA checklist for systematic reviews (Page et al., 2020). Methods: A comprehensive search of the literature published in Medline and CINAHL databases between 1999 and 2020 was undertaken in May 2019. The studies selected for this review (n = 18) were analyzed thematically. The validated Mixed-Methods Appraisal Tool assessed quality of the quantitative, qualitative and mixed methods studies. Results: The role of the observer in simulation was explored and included observation to transform practice in self and observation to transform practice in others, namely peers in the nurse role in simulation. Application of the MMAT indicated that of the 18 studies included only 6 (33.3%) had a clear research question. Research aims or objectives were found in another six studies (33.3%). In this review 13 studies (72%) included answers to the research question or aim, three (17%) did not and in two (11%) it was impossible to tell. Conclusions: Results of this review indicate the paucity of research relating to nursing student's experience of clinical reasoning while observing simulation. Further, it highlights the value of nurse educators optimizing the observer role and maximizing learning by scaffolding observer activities within the simulation experience.