Each delegation consists of up to four students and two mentors (one of them is designated as the head of the delegation or "head mentor"). A delegation may also include a handful of guests and scientific observers. Students must be under the age of 20 and must not be enrolled as regular students in any post-secondary education institution. The International Information Center of the International Chemistry Olympiad is based in Bratislava, Slovakia.

Countries who wish to participate in the IChO must send observers to two consecutive olympiads before their students can participate in the event. A total of 68 countries took part in the 38th IChO: 67 as participants and 1 as an observer.

The competition consists of 2 examinations, a theoretical examination and an practical examination. Both have durations of up to 5 hours, and are held on separate days with the practical examination usually being before the theoretical examination. The theoretical examination has a value of 60 points and the practical examination has a value of 40 points. Each examination is evaluated independently from the other and the sum of the results of the examinations determines a participant's overall result. A scientific jury, which is installed by the host country, suggests the tasks. The international jury, which consists of the 2 mentors from each of the participating countries, discusses the competition tasks and translates them into the language of their students' preference.

Students receive the examinations translated into their languages of preference. It is the duty of the mentors to translate the examinations from English before they are given to the participants. After the examinations are held and evaluated by a committee appointed by the host country and before awards are presented, mentors discuss the evaluation of the exams with judges of the committee to assure fairness in their evaluation. Because the mentors review the examinations before they are given to participants, any communication between the mentors and the students is strictly forbidden prior to the completion of both exams.

The syllabus of the competition contains subjects from several areas of chemistry, including organic chemistry, inorganic chemistry, physical chemistry, analytical chemistry, biochemistry, and spectroscopy. Though the majority of these subjects are included in most secondary school chemistry programs, for the most part, they are evaluated at a much deeper level and many may require a level of knowledge and understanding comparable to that of post-secondary education. In addition, the host country of each IChO issues a set of preparatory problems well in advance of the competition every year. These preparatory problems cover specific topics in considerable more depth than typical post-secondary education. Preparation for the International Chemistry Olympiad demands a high level of understanding and interest in chemistry and an outstanding ability to relate chemical subjects with one another as well as with the practical world.

All participants are ranked based on their individual scores and no team scores are given. Gold medals are awarded to the top 10% of students, silver medals are awarded to the next 20% of students, and bronze medals are awarded to the next 30% of students. Honorable mentions are awarded to participants that do not win a medal but score a perfect problem in either the theoretical or the practical examination. One special award is given to the student that achieves the highest score overall. Two separate special awards are given to the students who get the best score in the theoretical and practical examinations. Occasionally, another special award is given to the top-scoring female student as well.

These events are also outstanding opportunities for the students to meet people from all around the world who share similar interests, to visit different places, and to get in touch with different cultures. As the aims of the competition establish, the IChO competitions help to enhance friendly relations among young people from different countries; they encourage cooperation and international understanding.