The following year, Melbourne Tramway & Omnibus Company opened the North Fitzroy Line along Collins Street between Spencer Street (Stop 1) and St Vincent's Plaza (Stop 12) on 2 October 1886.

On 13 September 1953, this was amended so that both tram services ran through the intersection of Park and Clarendon Street instead of both turning, resulting in St Kilda Beach becoming the terminus of route 12.

[1] The first ever use of the route number 12 was for a about a year for the West Preston to St Kilda Beach service from 21 November 1929.

[1] In mid-2000, W-class trams were temporarily removed from service due to brake issues.

However, the peak-hour service was deemed unnecessary for the low-density and affluent suburbs in which it ran and on 18 November 2002, route 12 was discontinued.

[5] During special events such as the Australian Open or the Australian Grand Prix, route 12 temporarily diverts via La Trobe Street and replaces route 30 which do not run during the events.

[6] The temporary diversion was also in place between 13 July and 7 November 2020, as part of a COVID-19 response plan to increase overall capacity in the city which introduced shuttle services of route 11.