Background <p>Prior research on health and work-related consequences of workforce restructuring have shown mixed findings. This study seeks to examine if organizational upsizing and downsizing is prospectively associated with sickness absence due to common mental disorders (SA-CMD) and/or with exposure to workplace offensive behaviors (i.e. workplace bullying and workplace violence/threats of violence), and assess if workplace offensive behaviors mediate any association between organizational upsizing/downsizing and SA-CMD.</p> Methods <p>This study used a prospective design, combining self-reported survey data from the Swedish Longitudinal Occupational Survey of Health and national register data covering the period 2010–2018 on 10 358 employed individuals. Logistic regression with generalized estimating equations was used to examine the associations between organizational upsizing/downsizing, offensive behaviors, and sickness absence due to common mental disorders. To examine the role of offensive behaviors in the association between exposure to upsizing/downsizing and sickness absence due to common mental disorders, mediation analysis was performed.</p> Results <p>We found that upsizing, but not downsizing, was significantly associated with a higher risk of workplace violence/threats of violence (ORadj: 1.2, 95% CI 1.0-1.3). However, neither upsizing nor downsizing was significantly associated with workplace bullying or with subsequent SA-CMD and the mediation analysis indicated no mediation.</p> Conclusions <p>Although this study did not find a link between organizational upsizing/downsizing and later sickness absence due to SA-CMD, it suggests that upsizing may be associated with certain types of workplace offensive behaviors. Further research is needed to explore the mechanisms associated with these dynamics.</p>