Booth picked up 65 caps after making her national team debut in 2002 at the age of 17. She most recently played for Sky Blue FC of the National Women's Soccer League.
"It just felt like it was my time to move on," she said in a phone interview from her hometown of Burlington, Ont. "I had been preparing myself for this and it seemed like it was the right time for me."
Booth had one of the shootout goals in Canada's victory over Brazil at the 2011 Pan Am Games in Guadalajara, Mexico. Canada tied the game late in the second half and won 4-3 on penalty kicks.
The veteran defender was initially listed as an alternate on the 2012 Olympic side but was later added to the team when injuries forced roster changes.
"The hardest part (about retiring) is leaving the people that I've been around for so long," she said. "They're like a second family to me."
Although she never featured in London, Booth proudly stood on the podium with her teammates to receive their bronze medals after a 1-0 win over France at Wembley Stadium.
"Just the group that I was with, I was just so thankful to be around them and to be a part of that team," she said. "Just throughout my whole career that's what I strived to do — just to look for the positive in everything and use that as motivation and try to better the people around me."
Of her 65 caps, 37 came as a starter.
Her lone goal for Canada came in a 4-0 win over Jamaica at the 2006 CONCACAF Women's Gold Cup. Canada won silver at that tournament.
Booth also helped Canada win silver at the FIFA U20 Women's World Cup in 2002 and the Women's Gold Cup that same year.
The 29-year-old played college soccer at the University of Florida. She started her club career with the Toronto Lady Lynx and also played for the Vancouver Whitecaps.
Booth joined Sky Blue FC as part of the NWSL's original national team player allocation process.
"We all want to thank Mel for her contributions to Sky Blue's inaugural NWSL season," Sky Blue FC coach Jim Gabarra said in a release. "Congratulations to Mel on a successful career and good luck in the next phase of life."
Booth has yet to finalize her future plans but intends to remain involved in the sport in some capacity.