(1) Exchanges with Song

Koryo and Song established friendly relations for a long time. Koryo enforced pro-Song policies in order to import advanced culture from Song, and Song wished to join with Koryo in order to confront the threat from the northern tribes, so exchanges were active.
Koryo began exchanges with Song under the reign of King Kwangjong, and later, many missions visited Song, dispatching large numbers of students and monks. Merchants also traveled to Song frequently. Kim Haeng-song and Ch'oe Han, students from Koryo, studied in Guozijian and Koryo's monk, Uich'on, studied Buddhist doctrines in Song and brought back many Buddhist books.
Before this, in the earlier stages of Koryo, Uit'ong and Ch'egwan sailed to China and engaged in many activities. Uit'ong became founder of the Ch'ontae-jong sect in Song and Ch'egwan arranged the fundamental creed of Ch'ontae-jong in the famous book entitled "The Creed of Ch'ontaesa".
Many Chinese subjects were naturalized as citizens of Koryo and engaged in activities in Koryo. Many were apt writers and became government officials in Koryo. Ssang Ki (Shuangji) during the reign of Kwangjong and Zhouzhu under the reign of King Mokjong are examples of such personages. The Song envoy, Xujing, wrote "A Pictorial of Koryo" introducing the things of Koryo to China and praising the celadon porcelains of Koryo as world masterpieces.
Trade was active between Koryo and Song; Koryo exported gold, silver, ginseng, mats woven with flower designs and works inlaid with mother of pearl and imported brocades, medicines and books from Song.
Song porcelains influenced the development of the celadon porcelain in Koryo, and the Taesong-ak of Song became the court music of Koryo.

(2) Exchanges with Qidan and Nuzhen

From the first stages after its founding, Koryo enforced a policy to march northward in order to recover the territories of old Koguryo. Thus, Koryo often clashed with the kingdom of Qidan which destroyed Parhae and ruled over Manchuria. Thus, exchanges between Koryo and Qidan were not active. Koryo exported grains and stationary and imported silver and fur from Qidan.
After the destruction of Parhae, the Mohe tribe lived in scattered groups throughout Manchuria as well as in the northern frontiers of Koryo. Some of them referred to Koryo as their parent country and offered gifts to Koryo as tribute. In the 12th century, Nuzhen became a powerful nation and founded the unified kingdom of Jin, and Koryo was subject to the threats of them.
For this reason, trade between Koryo and Nuzhen began, but not actively. Koryo imported silver, fur and horses from Nuzhen and exported farm implements and grains.

(3) Contacts with Islam

The islands of the Saracen Empire in southwest Asia engaged in active trade with China, and the Arabian merchants of the Saracen Empire carried on commerce with Shilla by sailing to Ulsan via China.
During the Koryo dynasty, large groups of Arabian merchants arrived at Pyongnan Island to engage in trade. Pyongnan Island prospered as an international trading port at the mouth of the Yesong River where Song and Arabian merchants brought mercury, spices and corals, and Koryo gave them gold and brocades in exchange. Through their visits, Koryo became known to the West and that is how Korea got its Western name.

(4) Exchanges with Yuan

In the 13th century, relations between Koryo and Yuan became closer, and they engaged in active cultural exchanges up to the mid-14th century. Visitors coming and going did not cease for 80 years and customs were exchanged.
Among the upper class of Koryo, Mongolian was spoken and Mongolian customs were practiced as the cultures of the two countries were mutually exchanged. Marriages were often contracted between the royal families of the two countries and a Koryo woman from the Ki family became Empress to King Shundi of Yuan.
King Ch'ungson of Koryo built Man'gwon-dang (Hall of Ten Thousand Books) in Yenching to facilitate scholarly exchanges between the two. Koryo's Yi Che-hyon and Yuan's Chao Meng-pu made their scholastic debutes in the Man'gwon-dang.
Later, many writers of Koryo often visited Yuan and exchanged their customs.
At that time, Yuan was a world empire and imported cultures from various countries. As a result, Koryo was able to import Saracen culture through Yuan, and the Saracen developments in science and technology, astronomy, mathematics and medicines were influencial in bringing about similiar developments in Koryo. For example, the astronomical observatory "Soun'gwan" was built, and observation equipment used for the study of astronomy was improved, while the Yuan almanac "Shuigkili" was imported. Metaphysics was introduced from Yuan and the scholars of metaphysics propelled many social and cultural reforms. The skills of gunpowder manufacturing and cotton cultivation were also imported from Yuan.
In these ways, the Koryo-Yuan exchanges gave rise to the development of much of the culture in Koryo.

(5) Exchanges with Japan and the Southeastern Islands

Between the 9th and 12th centuries, diplomatic relations with Japan had been severed, but with the weakening of the Japanese legal system, local Japanese military officials began to grow in power and the Daimyo's or local lords' post-military forces expanded their power in the west. Thus traders of western Japan and Tazaifu actively engaged in relations with Koryo. Japanese envoys and merchants brought sulphur and mercury to Koryo while Koryo sent them the Taejanggyong, books and ceramics to be used for tea ceremonies.
In the latter period of Koryo, relations with Japan deteriorated. The expedition of Koryo-Yuan allied forces to Japan failed and the repeated invasions and attacks by Japanese pirates meant huge losses for Koryo. Pak Wi, during the reign of King Ch'ang, once attacked Tsushima, one of the island posts of Japanese pirates and overturned the pirate forces in 1389.
In the last days of Koryo, the Loochoos and Thailand of southeast Asia sent envoys to Koryo to offer their native products, and Koryo returned the gesture by also sending them gifts. In this way, there were some exchanges with the Loochoos and Thailand.