The start of the school dates back to 1999 with an enrollment of about 100 students in grades kindergarten through 3. The school’s founder was Mrs Jawaher al Hurgan and Madam Shirani Ibrahim (Nalifa) and the first principal was Mrs. Amira. Even though the school building was limited in a large flat, the wise administration of the founders started to achieve a clear success. The school’s enrollment increased steadily since then, and due to increasing development in Riyadh, Horizon International School’s capacity went from less than 30% to over 70% between 2000-2005. That was the core brick of the school’s blast off among the other international schools. The principal did her very best to make a good name for the school, and the community started to realize the quality service introduced by the school. Later, a new principal came to steer the wheel of the school but didn't stay more than two years. In 2007, Mr. Ghaith, the current principal, came to the lead and started a new era of the school history. Under his wise leadership, the school started to achieve a great success. In the first year of his administration and in response to the ministry laws, the school started applying a full segregation process by which the school was distributed into three separate divisions: the boys section, the girls section, and the kindergarten section. Furthermore, with the assistance of the school staff, the leadership team founded the basis of the school as being a well- organized educational association that assists in providing the community of Saudi Arabia with an elegant service. In 2010, the school reached its full capacity, about 7500 students. From that time until now, the school is still witnessing several ongoing developments. In 2013, the success of the school was crowned by acquiring the WASC accreditation. This accreditation opens the gates for the school students to get accepted into the international world of education. Nowadays, the school is standing as one of the prominent international schools in Riyadh.