Dieback symptoms have been increasingly reported in Chilean vineyards over recent years. Although there have been studies on Botryosphaeriaceae species and associated trunk disease incidence and severity in table grape-producing vineyards, their impacts on ‘Cabernet Sauvignon', the most planted red wine grape in Chile, is unknown. This study determines the fungus species, incidence, disease severity, and yield losses associated with Botryosphaeria dieback in Chilean ‘Cabernet Sauvignon' vineyards. Nine vineyards were surveyed during two growing seasons (2010 and 2018), and symptomatic wood samples were taken. Total potential production and yield losses were estimated from spur counts (2010) from harvested vines (2018) with different degrees of infection. Overall disease incidence was 87% in 2010 and 84% in 2018. Severity was 49% in 2010 and 47% in 2018. Yield losses were 39% in 2010 and 46% in 2018. Diplodia seriata was the most prevalent fungus isolated from symptomatic plants in both growing seasons. This study highlights the impacts of grapevine trunk diseases in vineyards in Central Chile, and indicates the need for improved disease management strategies.