A by-election was held for the Australian House of Representatives seat of Cook on 21 May 1955. This was triggered by the death of Labor MP Tom Sheehan.
The by-election was won by Labor candidate Jim Cope. The governing Liberal Party did not nominate a candidate, which resulted in Cope receiving over 85% of the first preference vote.
| Party | Candidate | Votes | % | ±% | |
|---|---|---|---|---|---|
| Labor | Jim Cope | 21,411 | 86.8 | +3.4 | |
| Independent | John Somerville-Smith | 3,248 | 13.2 | +13.2 | |
| Total formal votes | 24,659 | 96.8 | |||
| Informal votes | 814 | 3.2 | |||
| Turnout | 25,473 | 76.0 | |||
| Labor hold | Swing | −3.6 | |||