Watts Cycling – A high-end shop located in Hannam-dong in Seoul. Ask for Danny for assistance in English. Rentals available.
Manello – Reputable bike shop located in Guro are of Seoul. English speaking and well-known in the ex-pat community for excellent bike fitting.
Awesome Bike – I don’t know much about this shop, but it has been recommended several times by people I know. Located in Yangjae-dong, it is good if you’re in the Gangnam area of southern Seoul.
Bike Works – Someone I know says this is another place with good English speaking service. The link is to a Naver Blog, so you might need Korean help navigating it and finding the information you’re looking for.
Bike Lab: A trusted friend says, “The owner speaks English and holds several mechanic certificates including wheel building. He’s also trained in bike fitting. His shop is a bike repair academy, but he has a small selection of Trek bikes and Bontrager accessories, among other odd bits. He’s very responsive and if he doesn’t have a desired part, he’ll get it from his distributors. He’s extremely friendly and you can send him a message anytime, he’ll respond quickly.” The shop is located in NE Seoul and the owner goes by the name James, though he is Korean: 010-8917-5337
Mike Bike – Mike Bike is an English speaking mechanic in Busan who has been working on bikes for years. He comes highly recommended by a friend who gets all his work done with Mike. Apparently he’s the only level 3 UCI mechanic in Korea.