In front of a capacity Essex County Ground crowd, the hosts won with nine balls to spare, despite a scare in mid-innings when fast bowler Matt Dunn struck twice in an over to remove Ravi Bopara and Mark Pettini after they shared in a stand of 51 in six overs.
Overall, though, the Surrey bowling proved too wayward to pose many problems as Essex hauled in 165 for four with nine deliveries to spare.
After Jesse Ryder was caught behind from the third ball of the innings sent down by Azhar Mahmood, Tom Westley thrived as he took full advantage of leg-side deliveries to hit a punishing 38 from 20 balls, with the help of one six and six fours.
His innings was cut short when Kevin O'Brien trapped him lbw, but his dismissal brought in Bopara to join Pettini and they quickly took the game away from Surrey with some fine driving and pulling.
The momentum checked when Bopara was removed lbw by Dunn for 24 from 19 balls, while Pettini was bowled for 42 from 29 to leave Essex 108 for four with eight overs remaining.
Ben Foakes quickly became another victim of O'Brien, caught and bowled off a skier, but Ryan ten Doeschate took charge to condemn a Surrey team on a run of four successive victories to defeat.
The Essex one-day skipper finished unbeaten with 40 from 32 balls to emerge with the man-of-the-match award.
Tom Curran conceded 34 runs from three overs, while O'Brien, despite his two successes, went for 32 from his three.
Surrey's total owed much to skipper Gary Wilson who, arriving after the loss of Kevin Pietersen for a single, contributed an unbeaten 63 from 44 deliveries with the aid of six fours.
O'Brien, who twice struck left-arm paceman Reece Topley for six, contributed 33 from 22 deliveries and it was while trying to clear the ropes for a third time against Bopara that he was caught at long-on by Ten Doeschate.
Jason Roy also struck two sixes, both straight drives against fast bowler Matt Salisbury, while making 29 from 24 balls before a wild swish against Bopara saw him lose his off stump.
But it was a night to forget for Pietersen, whose solitary run came from 11 deliveries, his dismissal coming when he was stumped off a wide down the leg side to provide left-arm spinner Tim Phillips with his only success.
A strangely subdued Pietersen had been lucky to survive much earlier in his brief stay.
He was almost run out at the non-striker's end before facing and was then left doubled-up when struck painfully and sensitively by a drive from Roy immediately afterwards, but recovered just in time to make his ground.
The Essex attack showed the value of line and length, something that was to elude the visitors in their vain attempt to protect their total.
Phillips conceded just 25 in his four overs while Bopara went for 29 in an allocation that also included the wicket of Roy when he breached the in-form opener's defence.
Essex head coach Paul Grayson said: "We kept our discipline and our skill levels when we bowled and that was pleasing.
"We are in really good form at the moment in white-ball cricket and always fancy our chances of chasing down a total."
Surrey spinner Gareth Batty had no complaints about the outcome.
"We didn't score enough runs, it's as simple as that," he said. "We needed more runs in the powerplay.
"But Essex played very well and fully deserved their victory."