The 1938 Ipswich by-election was held when the incumbent Conservative MP, Sir John Ganzoni, was elevated to the peerage. The Labour Party gained the seat from the Conservatives.
| Party | Candidate | Votes | % | ±% | |
|---|---|---|---|---|---|
| Labour | Richard Stokes | 27,604 | 53.0 | +10.3 | |
| Conservative | Henry Willink | 24,443 | 47.0 | −10.3 | |
| Majority | 3,161 | 6.0 | N/A | ||
| Turnout | 52,047 | ||||
| Labour gain from Conservative | Swing | ||||