Farrell put in his most impressive union performance to date
Northampton: (7) 13
Pens: Howard (2)
Saracens: (21) 35
Tries: De Kock, Farrell, Vyvyan, Skirving (2)
Cons: Jackson (5)
Andy Farrell's first top-level score since switching codes was one of five Saracens tries as Northampton were hammered at Franklin's Gardens.
Vaughan Going put the home side in front after 20 minutes but Farrell's kicking then gave Saracens control.
Scrum-half Neil de Kock levelled for Sarries and Farrell then broke two tackles to put the visitors in front.
Hugh Vyvyan went over before the break and Ben Skirving added a fabulous breakaway try and another late score.
Two Johnny Howard penalties had hauled Northampton back into the game early in the second half but for the most part it was one-way traffic from the visitors.
Saracens coach Adrian Kennedy: "We're very happy with Andy Farrell. He showed the right qualities to succeed at inside centre and he's developing his game sense all the time.
"He's an incisive runner and he ran some great lines and his kicking from hand was also superb - he's capable of playing at the highest level.
"To come to Franklin's Gardens and to win is fantastic, we're delighted. We had a sluggish start, not for the first time this season, and it's something that we're addressing.
Northampton head coach Paul Grayson: "Andy Farrell has been so unlucky with injuries. If he hadn't had the car crash then I think he could be going to the World Cup.
"If he had played 12 since the beginning then it would be different.
"I am disappointed with the margin of the defeat but we had the chance during the second half to go under the posts but we couldn't get through."
Northampton: Going; Howard, Myler, Mallon, Diggin; Spencer, Robinson; Smith, Thompson, Budgen, Damien Browne, Gerard, Tupai, Fox (capt), Easter.
Replacements: Hartley, Tonga'uiha, Lord, Daniel Browne, Vass, Harries, Wyles.
Saracens: Castaignede; Scarbrough, Sorrell, Farrell, Vaikona; Jackson, de Kock; Yates (capt), Byrne, Visagie, Ryder, Chesney, Vyvyan, Seymour, Skirving.
Replacements: Cairns, Liffchak, Fullarton, Gustard, Dickens, Penney, de Vedia.