Highland Park has three Sister Cities; Ferrara, Italy, established in 1989, Puerto Vallarta, Mexico, established in 2001, and Modena, Italy established in 2009. Highland Park's sister city relationships were forged through cooperation with Sister Cities International, based in Washington D.C., who helped match Highland Park with the two cities. In 2006, Highland Park also formed a friendship cities relationship with Kiryat Gat, Israel. A sister city link develops when an American community of whatever size or character links with a community in another nation. The goal for the cities involved is to learn more about each other and to develop exchanges.

As sister cities, citizens and organizations are involved in the exchanging of ideas, cultures and people. Highland Park, Puerto Vallarta, and Ferrara have participated in several exchanges since the relationships were forged. Several organizations from Highland Park have traveled to both Puerto Vallarta and Ferrara, including a contingent from a tennis organization who played in a tennis tournament, the Highland Park Strings, and student groups from Highland Park High School. Conversely, several contingents have traveled from Puerto Vallarta and Ferrara to Highland Park, including a group of 40 young people from Italy who sang and danced Italian music from the 1950s through the 1980s and a group of artists who participated in the 2005 Port Clinton Art Festival. Plans are currently underway to establish exchanges with Kiryat Gat. A group of school children from Kiryat Gat visited Highland Park in 2006 and were given a tour of the City.

The Sister Cities concept was initiated by President Eisenhower in 1956 to establish greater friendship and understanding between the United States and other nations through direct contact.