Pereyra, who scored five goals in 18 league appearances for Watford last season, volleyed home from a corner by Jose Holebas in the 35th minute before doubling the lead with an unmarked finish in the 54th.
"The first half was hard".
However, they scored from both, and never looked like letting their advantage slip.
N'Golo Kante got Chelsea up and running, with a cool Jorginho penalty doubling their lead before Eden Hazard came off the bench to tee up Pedro for the third.
Huddersfield felt hard done by because they believed that Christopher Schindler's boot-to-boot contact with Marcos Alonso was accidental.
"I am really very happy because in the first part of the season I think it is not easy for us to gain points", Sarri said.
Jorginho, whose passing was near-faultless throughout, feinted during his run-up before rolling the ball in, leaving the goalkeeper flatfooted.
Pedro applied the finishing touch after Hazard accelerated forward with objective before unselfishly teeing up the Spaniard, who was cool and collected before lifting the ball over the onrushing Hamer, watching it trickle into the corner.
GK Kepa Arrizabalaga, 7 - Making his debut just three days after signing for a club-record fee, there were questions about his familiarity with Sarri's style of play and the defence in front of him, but the 23-year old looked assured in goal and a confidence-boosting clean sheet came easily enough.
Quite how David Luiz will manage in a flat back four is open to debate.
It was Huddersfield's only shot on target in the opening period, but Kepa was relieved to see a Steve Mounie header off the post and eventually get cleared from danger.
Huddersfield, meanwhile, have another tough matchup ahead and will play Manchester City away next weekend.
The Terriers, meanwhile, were probably buoyed by the fact that their survival last season was helped by the point they gained against the Blues in their penultimate game of the campaign.
Chelsea Give Bakayoko The Blues With Milan Loan
Bakayoko featured in all of Chelsea's pre-season games but was absent in the Community Shield encounter against Manchester City . At a press conference, Sarri told reporters: "Now I think the squad is too large". "But I don't know who at the moment".
Partial Solar Eclipse Occurs Saturday! What to Expect
This is caused by retinal burns which occur when the powerful rays of the Sun damage cells in the back of the eye. The Aug. 11 eclipse marks the end of this eclipse season after two previous eclipses during the month of July .
Indonesia quake death toll almost triples to 347
Indonesia's chief security minister had earlier said 319 people had died, while local media have reported figures as high as 347. The official death toll from the initial quake stood at 321 as of Friday, according to Indonesia's mitigation agency (BNPB).
Gaza rocket hits near southern Israeli city in show of defiance
The Israeli military said seven people were wounded by Palestinian rockets and mortars that hit southern Israel across the border. Palestinians look at damage at the site of an Israeli air strike in Al-Mughraqa on the outskirts of Gaza City, Aug. 9, 2018.