The 48-year-old singer - who raises children Leni, seven, Henri, six, Johan, five, and two-year-old Lou with his wife - and the supermodel dressed as primates for a Halloween party in New York last month and the musician insists he still finds his spouse attractive when she dons fancy dress costumes.
He told Closer magazine: "Heidi was the sexiest ape ever. I'm never keen on my outfits, but I really liked Heidi's last year when she went as an android and wore stilts. She looked fantastic, but I spent the whole evening trying to keep her upright.
"Of course I fancy her just as much on the red carpet as I do as an android but, more than anything, it's just a lot of fun. Heidi's always been up for a party."
While Seal and Heidi enjoy dressing up for fancy dress parties, the 'Project Runway' host has previously insisted their love of costumes does not extend to the bedroom.
She has said: "I'm not big on costumes in bed, to be honest. I wouldn't say no if he wanted to try, but it seems so inorganic. Maybe it'll come later - in five or 10 years, I'll start buying funny outfits. But for now, we're nice and spicy in that department."