The 24-year-old "Thinking Out Loud" hitmaker and Seaborn were seen walking side by side in New York before he left for his 'X' world tour, reported Aceshowbiz.
Sheeran was seen wearing a long-sleeved dark blue shirt and black trousers while the his friend wore a crop top and light blue jeans.
The duo also enjoyed a baseball game in Queens.
Neither of them has commented on their rumoured romance.
Sheeran and Seaborn came in touch with each other during their days at Thomas Mills High School in Framlingham, Suffolk.