Witnesses told People that William, 36, and Harry, 34, didn't speak to one another outside of St. George's Chapel in Windsor, neither before nor after church.
One spy, however, caught the brothers exchanging pleasantries briefly in a video posted to Instagram.
The princes' cousin and her husband, Zara and Mike Tindall, reportedly sat between William and Harry at church. William's wife Kate Middleton was also present.
Heavily pregnant Meghan Markle is on maternity leave and wasn't in attendance.
A source told Entertainment Tonight that Harry and William are at "different stages in their life" and are "no longer the boys" the world knew when they were growing up. The insider also noted that the gentlemen sat apart from one another at the premiere of "Our Planet" earlier this month.
The feud was reportedly sparked when Prince William expressed concerns over how fast Prince Harry and Meghan, now Duchess of Sussex, moved in their relationship.
The awkward Easter outing comes on the heels of reports that Harry and Meghan may work abroad in Africa at the behest of William, who allegedly wants to keep the spotlight on the Cambridges.
Kensington Palace didn't deny the rumors of the Duke and Duchess of Sussex potentially working overseas, but said in a statement, "Any future plans for the Duke and Duchess are speculative at this stage. No decisions have been taken about future roles. The Duke will continue to fulfill his role as Commonwealth Youth Ambassador."