The Old Markhamian Association (OMA) was founded in 1950, in the early beginnings of Markham College, and remains an integral part of the school.
The OMA Board is responsible for organising a yearly calendar of social, sporting and cultural events including the annual alumni luncheon where hundreds of Old Markhamians attend every year as well as the Golden and Silver Jubilee celebratory cocktails.
The present Board of the OMA is comprised of the following members:
| - Mr. Luis Huaynas (Promotion 1999) | President |
| - Miss María Claudia Parró (Promotion 2004) | Vice President |
| - Mr. Claudio Cavassa (Promotion 1992) | Treasurer |
| - Mr. Sandro Ascenzo (Promotion 1986) | Secretary |
| - Mrs. Melissa Hajek (Promotion 2010) | Director |
| - Mr. Ricardo Coda (Promotion 2001) | Director |
