Goals from Pablo Counago and Jonathan Walters saw Ipswich close in on the top six with victory over Derby.
Counago marked his first league start for a month by guiding a low shot into the corner from 12 yards out.
Both sides squandered chances and after an hour Przemyslaw Kazmierczak almost brought Derby level when Richard Wright tipped his header over the crossbar.
But Walters sealed the win when he swept home David Wright's cross for only his second league goal this term.
Ipswich manager Jim Magilton told BBC Radio Suffolk:
"I thought defensively we looked pretty sound, it's nice to have a clean sheet.
"Everybody looked pretty composed at the back, we had a few 'hairy scary' moments but you expect that against a good side like Derby County with the quality they have up front.
"We took our chances and are very pleased that the two strikers scored."
Derby manager Paul Jewell:
"It was one of our worst displays for a while - the type of performance I thought we'd left behind.
"I'm at a loss to explain it. I'm not the type of manager who brushes things under the carpet and says it was a bad day at the office. It just wasn't acceptable.
"We weren't strong mentally or physically and, given the manner of their first goal, after a catalogue of errors, it was always going to be an uphill struggle."
Ipswich: Richard Wright, David Wright, Bruce, Naylor, Thatcher, Norris (Miller 82), Shumulikoski, Garvan, Ambrose, Walters (Lisbie 89), Counago (Stead 74).
Subs Not Used: Supple, Balkestein.
Booked: Naylor.
Goals: Counago 27, Walters 66.
Derby: Carroll, Connolly, Davis (Powell 36), Nyatanga, Stewart, Barazite, Green, Addison, Commons (Kazmierczak 50), Hulse, Villa (Ellington 70).
Subs Not Used: Bywater, McEveley.
Booked: Nyatanga, Connolly.
Att: 20,239
Ref: Mike Russell (Hertfordshire).
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