Left ventricular diameter (LVEDD) increases with systematic endurance training but also in various cardiac diseases. High exercise capacity associates with favorable outcomes. We hypothesized that peak work rate (Wpeak) indexed to LVEDD would carry prognostic information and aimed to evaluate the association between Wpeak/LVEDDrestand cardiovascular mortality. Wpeak/LVEDDrest(W/mm) was calculated in patients with an echocardiographic examination within 3 months of a maximal cycle ergometer exercise test. Low Wpeak/LVEDDrestwas defined as a value below the sex- and age-specific 5th percentile among lower-risk subjects. The association with cardiovascular mortality was evaluated using Cox regression. In total, 3083 patients were included (8.0 [5.4–11.1] years of follow-up, 249 (8%) cardiovascular deaths). Wpeak/LVEDDrest(W/mm) was associated with cardiovascular mortality (adjusted hazard ratio (HR) 0.28 [0.22–0.36]), similar to Wpeakin % of predicted, with identical prognostic strength when adjusted for age and sex (C-statistics 0.87 for both). A combination of low Wpeak/LVEDDrestand low Wpeakwas associated with a particularly poor prognosis (adjusted HR 6.4 [4.0–10.3]). Wpeak/LVEDDrestwas associated with cardiovascular mortality but did not provide incremental prognostic value to Wpeakalone. The combination of a low Wpeak/LVEDDrestand low Wpeakwas associated with a particularly poor prognosis.