To determine the size at which choroidal melanomas can metastasize and to report the characteristics of small fatal choroidal melanomas (SFCM). Retrospective case series. Ten ocular oncology services submitted 45 patients with a choroidal melanoma 3 mm or less in thickness and 9 mm or less in largest basal diameter (LBD), when treated, who developed metastases. Median tumor thickness was 2.4 mm (range, 1.0–3.0 mm) and LBD 7.3 mm (range, 3.0–9.0 mm). Of 14 (31%) tumors that were first observed, 12 grew a median of 0.5 mm (range, 0.1–1.2 mm) in thickness and 1.0 mm (range, 0–3.0 mm) in LBD within a median of 7 months; 3 were initially smaller than 3 mm in LBD. Number of risk factors for growth and metastasis was 0 for 4% of the tumors; 60% were over 2 mm in thickness, 63% had subretinal fluid, 84% caused symptoms, 57% had orange pigment, and 92% were within 3 mm of the disc. Local recurrence occurred in 8 of 31 eyes (26%) treated conservatively. Median metastasis-free survival was 4.5 years (range, 0.8–15.7 years). Kaplan-Meier estimate of metastasis developing was 15% (95% confidence interval CI, 7–26), 51% (95% CI, 36–64) and 85% (95% CI, 71–92) by 2, 5, and 10 years, respectively. By the time of analysis, 37 patients had died of metastasis after a median of 7 months. Choroidal melanomas less than 3.0 mm in LBD are highly unlikely to metastasize. Risk factors of an SFCM are similar to those for all choroidal melanomas of similar size. •Choroidal melanomas more than 3.0 mm in diameter are able to metastasize.•Observation beyond this size limit may alter survival.•Small fatal melanomas appear clinically similar to reported small nonfatal ones.