Jorunna funebris is one of the nudibranch species with the largest distribution worldwide, but there is lack of information about its life history. To provide more information on embryonic development, 19 adult nudibranchs ranging in length from 1.3–6.5 cm were collected from the Gulf of Thailand for examination of embryonic development under laboratory conditions. The seawater conditions in the broodstock aquaria were as follows: temperature range, 22.3–26.3°C; salinity, 27.9–34.0 psu; dissolved oxygen, 7.0–8.3 mg/L; and pH, 7.2–8.9. Each nudibranch laid only 1 egg mass after culturing for 1–3 days. The egg masses of J. funebris ranged from 17.1–48.0 cm in length, and between 0.4 cm and 0.7 cm in width. The density of egg capsules varied from 27–64 egg capsules/mm² of egg mass (n = 4), and each egg capsule had 1–4 larvae inside (n = 9). The embryonic period (expressed as the mean ± SD) was 7.3 ± 1.0 days (n = 7 egg masses). Based on the results of uncleaved embryonic diameter, embryonic period, and shell pattern, the development mode of J. funebris could be defined as “planktotrophic development.”