The 25-year-old from North Wales gave what he described as his best display "for some time" to beat the defending champion, Neil Wilson.
"The triple lutz was huge. Maybe I was too charged up. I really wanted to do well and I nearly crashed into the barrier," a smiling Cousins said.
In contrast, Wilson's triple axel combination was slightly flawed, but this was only the second time the 19-year-old from Belfast had tried the difficult three-and-a-half turn in competition.
Meanwhile, in the senior women's event Zoe Jones, who was given the chance to prove she was worthy of Olympic selection at this event, withdrew due to injury just prior to the short programme.
The 17-year-old, runner-up for the past three years, left the arena after early-morning practice in tears, but returned last night to cheer on her Swindon rink-mate Jenna Arrowsmith.
"It's not a bad, bad injury," Lesley Norfolk Pearce, who coaches both girls, said. "She tensed up on a jump and pulled a hamstring at the top of her left leg.Having all this publicity about the Olympic selection put so much pressure on her."
Jones was told by the British Olympic Association that in order to go to the Games next February she had to land two triple jumps yesterday and four in today's final.Reuse content