Saracens came from behind to defeat London Wasps 34-28 at Twickenham in the English Premiership this weekend.
Trailing 28-20 heading into the final quarter, David Strettle scored two late tries as Hargreaves picked up his first win since taking over the captaincy from Steve Borthwick at the conclusion of last season.
South African flanker Ashley Johnson had earlier played a key role in Christian Wade's second try, as Wasps threatened an upset.
There were plenty tries across the board on the opening weekend, with George North grabbing a hat-trick as defending champions Northampton Saints got their title defence off to a flyer with a 53-6 win over Gloucester.
Elsewhere, Chrysander Botha got a late try as Exeter Chiefs demolished London Welsh 52-0, while there were also wins for Bath, Leicester and Harlequins.
Round 1 results:
Northampton Saints 53 Gloucester Rugby 6
Sale Sharks 20 Bath 29
Saracens 34 London Wasps 29
Leicester Tigers 36 Newcastle Falcons 17
London Irish 15 Harlequins 20
London Welsh 0 Exeter Chiefs 52