The actor told TV Line that the pair are unlikely to rekindle their romance in the CBS sitcom's seventh season.
"[Barney and Robin are] a good match," he admitted. "So I think there might be some long-distance pining for a little while on the show. I don't think they're going to end up back together, at least any time soon."
Harris also suggested that Barney, who is currently dating Nora (Nazanin Boniadi), will be back in "player mode" in future episodes.
"Barney's growth in season six was more emotional and his growth in season seven will be more... genital," he quipped.
How I Met Your Mother co-creators Carter Bays and Craig Thomas previously insisted that the identity of Barney's mystery bride will be revealed in the new season.
"We're not going to string that along," said Thomas. "[The identity of the bride is] the big central question, though there are many, many new questions."
The comedy returns to CBS on Monday, September 19.
> Jimmi Simpson to guest in How I Met Your Mother
Watch a promo for How I Met Your Mother's new season below: