Farah's last results saw him finish eighth in the Great Manchester Run 10K in May and ninth in the London Marathon the previous month.
The Big Half was Farah's last race in London, with the final race of his career taking place at the Great North Run on Tyneside next weekend.
Jack Rowe came first in the elite men's race with a time of 01:01:08, narrowly edging out fellow Briton Mahamed Mahamed who finished in 01:01:16. Andrew Butchart was next to cross the line before Farah finished with a time of 01:02:43.
Calli Thackery finished first in the women's elite race, with David Weir earning the top spot in the wheelchair race.
Farah reflected on an “emotional” day as his career approaches its end next Sunday.
He told BBC Sport: “It was quite emotional today because I haven't been feeling well this week, I've got a bit of a cold. I didn't know if I could do the race, then I was thinking about all the people coming out here and I'm not going to get another chance.
“I came out today, gave it my best but you can't take anything away from Jack, he's been working hard for the last three years and he's deserved that win.
“It's just nice to see youngsters coming along, grabbing that chance and believing in themselves. As I said, when you've achieved everything it must come to an end at some point. I'm getting on a bit and I'm kind of just looking forward to taking a break and hopefully being involved in sports, but just spending time with my family.
“Honestly, without the crowd and support I've had over the years it wouldn't be the same.”
Race winner Rowe added: “I'm super happy. I've been out training hard with Mo and his team and some guys I go out with.
“It was nice to come back and deliver, it feels smooth out there and I enjoy running out on the roads in London."