The Tolka rises east of Dunshaughlin,[3] County Meath, and by-passes Dunboyne, from where it receives the Castle Stream tributary.

There are at least fourteen infalls within Dublin City boundaries (the count is complicated by connections with the Wad River system).

Fingal County Council area tributaries include the East and West Pinkeen Streams, and another waterway in semi-rural Dublin.

[4] The last few tributaries connect to the tidal part of the Tolka, or its estuary, but have been confused by the merging of natural watercourses and city drainage lines.

The river Tolka itself for miles in either direction is in a filthy condition and our "clear stream" in joining it carries even more dangerous pollution into an already poisonous flow of water".

It passes initially through the Tolka Valley Linear Park near Blanchardstown, then between trees north of River Road, then along the southern edge of the Tolka Valley Park in the western City Council area, where it receives a tributary which provides the source of water for a pond featuring considerable birdlife, including swans, ducks and herons.

A large landscaped pitch and putt facility operated by Dublin City Council is situated on the southern side of the park, just south of the meandering river.

[8] In early December 1954, the River Tolka flooded areas in Glasnevin, Drumcondra, Fairview, Ballybough, North Strand and East Wall.

The river holds a large stock of small wild brown trout, this is topped up a few times a year by the angling club for competitions.