England stuttered to victory in their Group B opener in Frankfurt thanks to a third-minute Paraguay own goal.
Carlos Gamarra put David Beckham's left-wing free-kick past his own keeper to set up a half dominated by England.
It was a different story in the second half as Paraguay threatened more as a cautious England put themselves under unnecessary pressure.
Frank Lampard came closest to extending the lead with two long-range efforts as the South Americans pressed for a draw.
England coach Sven-Goran Eriksson will be happier with the points than the performance.
But England will not complain, and rightly so with their history of making slow starts to major tournaments.
Steven Gerrard, as expected, was declared fit after a back injury to give England a full-strength side apart from Wayne Rooney.
And if they needed a lift in the searing heat, it came after only three minutes courtesy of Beckham's free-kick.
England's captain swung in the set-piece and it glanced off the head of Gamarra and beyond the despairing dive of keeper Justo Villar.
Villar's afternoon got worse two minutes later when he was injured making a clearance and limped off with what looked like an ankle injury.
His replacement, Aldo Bobadilla, did not fare much better, and was penalised for time-wasting, only for Lampard to fail to take advantage of the free-kick 15 yards out.
Nelson Valdes was a threat to England, and he shot wide after a slip by John Terry - with Gerrard shown a yellow card for a tackle as the Paraguayan shot.
England were in confident mood and Bobadilla saved from Lampard as they dominated proceedings, Beckham also shooting narrowly off target.
But Paraguay grew in confidence and goalkeeper Paul Robinson was glad to see another shot from Valdes fly narrowly wide on the stroke of half-time.
606 VIEW
England were subdued after the break, and Eriksson decided to make a change after 55 minutes, sending on Stewart Downing for a subdued Michael Owen.
Paraguay were gaining heart from the fact that Eriksson's side had not killed them off, and Roberto Acuna gave England an anxious moment on the hour with another shot just off target.
England's response was a cross-shot from Beckham that flew across the face of goal, and an effort from the lively Joe Cole that was dragged wide.
Paraguay had possession without mounting a serious threat, and Lampard could have doubled England's advantage, only to be denied by two fine saves from Bobadilla.
England held on to deservedly pick up three points, but there will undoubtedly be tougher tests ahead.
England: Robinson, Neville, Ferdinand, Terry, Ashley Cole, Beckham, Lampard, Gerrard, Joe Cole (Hargreaves 82), Owen (Downing 56), Crouch. Subs Not Used: Bridge, Campbell, Carragher, Carrick, Carson, James, Jenas, Lennon, Rooney, Walcott.
Booked: Gerrard, Crouch.
Goals: Gamarra 3 og.
Paraguay: Villar (Bobadilla 8), Caniza, Gamarra, Caceres, Toledo (Nunez 82), Bonet (Cuevas 68), Acuna, Paredes, Riveros, Valdez, Santa Cruz. Subs Not Used: Barreto, Cabanas, Da Silva, Dos Santos, Gavilan, Gomez, Lopez, Manzur, Montiel.
Booked: Valdez.
Att: 48,000
Ref: Marco Rodriguez (Mexico).
Fifa man of the match: Frank Lampard.
TRIVIA
This was the fifth time in 12 World Cup appearances that England won their opening match. The game was decided by the 30th own goal in the history of the World Cup. Carlos Gamarra became the first player from Paraguay to concede an own goal in the tournament finals. It was the second time England have been beneficiaries of an own goal. They beat Czechoslovakia 2-0 in 1982, courtesy of an effort from Trevor Francis and an own goal from Jozef Barmos.
Michael Owen became the first English player since the 1990 finals to gain at least 10 World Cup appearances. David Beckham earned his 90th career cap, tying him for fifth place on the all-time English list with Bryan Robson, and by making their appearances, both Beckham and Owen have now seen action at three different World Cups, tying the English record held by seven other players.
Roberto Acuna, Denis Caniza, Carlos Gamarra and Carlos Paredes set the Paraguayan record with an appearance at three different World Cups.