Lawes and Morris leapt around the arena after dominating the final of the mixed doubles, which was making its Olympic debut, against Swiss pair Jenny Perret and Martin Rios.
Earlier, husband-and-wife team Anastasia Bryzgalova and Aleksandr Krushelnitckii beat Norway’s Kristin Skaslien and Magnus Nedregotten 8-4 to take bronze.
“It’s very important that we are family,” Bryzgalova said. “That was very important in order to survive yesterday’s loss.
“Just to come out here today and to make the match that we can be proud about. The fact that we are family helped us a lot.”