Barry's opener came from Steven Gerrard's cross to the far post after a short-corner routine caught out the home defence, and further strikes from Emile Heskey, Wayne Rooney and a Frank Lampard penalty made it six group wins out of six.
Gareth Barry celebrated his £12million transfer to City by grabbing the all-important opening goal for England in Kazakhstan - and then admitted that his Blue move had taken his mind off preparations.
Midfielder Barry's rare header after 39 minutes was only his second England goal and put Fabio Capello's side on the way to a 4-0 qualifying win in Almaty that kept up our 100 per cent record at the top of the table.
He said: "That was a special moment, I don't get many headers so I was delighted to see that one creep in. But I'd be lying if I said I wasn't distracted earlier on in the week because I had other things on my mind.
"But as soon as it was all signed I had a chat with the manager and he just said, 'concentrate on the game and focus'. We're professionals and there was a job to do. Thankfully, we've come away with three points."
Barry added: "The first goal is always important in any game. Kazakhstan had started so well, they were lively and they were in and around us, so I was really pleased to get the goal and settle us down."
The only downside to the biggest week in Gareth's career was a 16th-minute booking, his second of the campaign, that will rule him out of Wednesday's match against Andorra at Wembley, ending his run of playing in every game of Capello's reign.
Barry's new City team-mate Shaun Wright-Phillips came off the England bench for the second half, while Wayne Bridge was one of the unused substitutes as England eased their way towards South Africa next summer.
Blues skipper Richard Dunne headed the Republic of Ireland in front against Bulgaria in Sofia but the lead lasted only four minutes before Shay Given was beaten to leave the final score 1-1 in Group Eight.
Dunne, being linked with summer bids by Spurs and Stoke, was Ireland's inspiration at the back. Neither Valeri Bojinov nor Martin Petrov were at their sharpest for Bulgaria and both went off around the hour mark.
The Irish crunch tie will be October's Dublin showdown with Italy, who remain group leaders by just a point.