Dundee agree deal for striker
Nish, who has had previous spells with SPL sides Hibs and Kilmarnock, has committed to the club on loan until at least the January 2013 transfer window.
The centre-forward travelled north of the border on Tuesday to prepare for training with his new team-mates.
The 31-year-old was linked with a loan move back to Kilmarnock earlier this month but the two sides were unable to agree terms.
Nish joined Hartlepool from Hibernian last summer but has slipped down the pecking order in recent times.