The Singapore team received five gold medals and was placed first out of 84 countries at the event held in Bangkok, Thailand from July 10 to 18.
The Ministry of Education said this was an improvement over Singapore's 7th placing last year.
The other teams that received five gold medals were from China, Korea and Taiwan.
The Singapore gold medallists are Kang Zi Yang, Li Kewei, Lin Jiahuang and Lin Sen of Raffles Institution; and Tan Zong Xuan of NUS High School of Mathematics and Science.
Meanwhile, Singapore received three gold medals and one silver medal at the 22nd International Biology Olympiad that was held in Taipei from July 10 to 17.
The Singapore team was placed third in a field of 229 students from 58 countries.
The gold medallists are Javan Lee Tze Han of Hwa Chong Institution; Hong Xinyuan of NUS High School of Mathematics and Science; and Jin Chentian of Raffles Institution. The silver medallist is Michael Sia Zhen Wei of Anglo-Chinese School (Independent).
At the International Chemistry Olympiad held in Ankara, Turkey from July 9 to 18, Singapore received four silver medals.
It was placed 17th in a field of 273 student participants from 70 countries.
The silver medallists are Chew Hong En, Guo Xiuzhen and Lim Yuan Zhi Martin of Raffles Institution; and Seet Hua En Ian of NUS High School of Mathematics and Science.