The old grandstand has been replaced with two stands with a total capacity of 5,000 spectators.
The state-of-the-art complex has an outdoor 400-metre track, an indoor track, offices and meeting spaces, and provides physiotherapy, massage, and strength and conditioning facilities for athletes.
Scotstoun is one of the arenas created for the 2014 Games,along with the planned National Indoor Sports Arena and the Sir Chris Hoy Velodrome.
Besides squash and table tennis, it will also be a training venue for athletes during the Glasgow Games.
The redevelopment of the stadium started in March 2008 and was funded with £14 million from Glasgow City Council and £4 million from sportscotland.
Scotstoun will become Glasgow Warriors rugby team's headquarters from June and will also become a centre of excellence for rugby.
This comes through a partnership between Scottish Rugby Union, Glasgow City Council and Culture and Sport Glasgow.
Glasgow City Council Leader Steven Purcell said: "Today marks the start of a new era for sport in Scotland, with the improved facilities further enhancing Scotstoun's international reputation as a world-class athletics venue.
"It is another great staging post in the legacy of facilities that will be built in Glasgow for the Games."
The Princess Royal praised "the attraction the stadium has for all range of users".
She said: "Not everybody wants to be an elite sports person so the need to keep this a friendly place that encourages everybody to come is crucial to its continuous use."
March 2008: Glasgow Commonwealth Games costs begin to rise