Interscholastic Association of Southeast Asian Schools

The first season of IASAS, held in October, includes soccer, volleyball, and cross country running.

The third season of IASAS, held in April, includes badminton, fastpitch softball (for women) and baseball (for men), golf, and track and field.

In fall 2019, International School of Manila held a 'Super IASAS', with all season one sports occurring in the same location.

The Leadership Convention, a conference for student peer-helper groups took place in September 2005, 2006, and 2007, but was discontinued during the 2008-2009 academic year due to the effort to reduce unnecessary travel for non-competitive events.

Cultural Convention (CC) is held in March and includes three separate events: "Music", "Dance, Drama, Art and Theatre Tech (Stagecraft)", and "Debate and Forensics".