<p>Potato spindle tuber viroid (PSTVd) is a small, single-stranded, and circular RNA molecule and is an important pathogen that significantly affects the production of tomato and potato. PSTVd is transmitted by seeds in tomato, potato and petunia; therefore, seed testing for PSTVd in these crops is necessary to prevent the spread of PSTVd to the uncontaminated regions or countries. Eggplant is also a host plant for PSTVd, and its seeds are widely produced and internationally traded; therefore, these seeds can spread PSTVd contamination. However, seed transmission of PSTVd in eggplants has not yet been reported. In this study, we investigated whether PSTVd is seed-transmitted in commercial eggplant cultivars and the World Eggplant Core (WEC) collection. Seed transmission to germinated eggplant seedlings varied among the progeny of infected plants, ranging between 0–64%. These results indicate that PSTVd-infected eggplants may carry the risk of transmitting the viroid. Contaminated seeds of WEC001 and WEC038 tested positive for PSTVd at 80–100% levels by reverse transcription–polymerase chain reaction, even after sodium hypochlorite treatment. Furthermore, in situ hybridization analysis showed that PSTVd was present in the endosperm of the PSTVd-contaminated seeds of WEC001 and WEC038. These results suggest that PSTVd inside the seed coat, such as endosperm, contributes to seed transmission.</p>