The second is due to start soon afterwards with both stages set to take about three months.
“When it opens, it’s going to be a fantastic asset for the community,” Jo Shore, from TfWM, said.
Residents and businesses were told of the disruption in writing and at drop-in sessions over the summer, a spokesperson for the West Midlands Combined Authority said.
They added that journey times into Birmingham New Street were expected to be about 10-15 minutes once the overall scheme was up and running.
Work has begun on the platforms and other buildings at Moseley Village along with the other two, Pineapple Road and Kings Heath, and a new footbridge was installed at the latter over the summer.