The Millennium Line is SkyTrain’s middle child line and mostly opened in 2002. Until the Evergreen Extension opened in 2016, it had one of the strangest operations of any transit line anywhere where trains originating at VCC-Clark (the end of the extension) pass through Commercial-Broadway's Lower Level run down the entire Millennium Line to Columbia and are then through routed on the Expo Line back through Commercial-Broadway (this time on the Upper Level) over the line they originated on making a full loop and into downtown Vancouver and the Waterfront. With the opening of the Evergreen Extension, the Millennium Line became a more typical transit route operating between VCC-Clark and Lafarge Lake-Douglas, with some expo line trains now branching to Production Way-University, taking over the former service at Braid and Sapperton.

The stations are significantly more modern looking than on the Expo with a large use of glass windscreens and station roofs that are designed to look wooden, almost the entire line runs on an elevated concrete guideway also noticeably more modern with a different emergency pathway design. Mark-II cars were ordered for the expanded rolling stock requirements for the Millennium Line but Mark-I cars are routed onto it interchangeably as well.