Conference organisers initially turned away 15 Iranian researchers from the Trends in Nanotechnology conference held this week in France.
The temporary ban has raised concerns about the international isolation that Iranian scientists could face over their country's uranium enrichment programme.
The organisers, who revoked the ban in July, blamed a series of misunderstandings over security-clearance rules caused by the political situation.
They say two of the researchers are attending the conference and the rest withdrew because of problems such as visa delays.
Reza Mansouri, a well-known Iranian physicist at the Sharif University of Technology in Tehran, complains that researchers from his country suffer discriminating visa delays and are being ostracised by fellow scientists.
But he believes that once the tense international climate settles down, scientists will return to more normal collaborations with Iranians, "bringing more rationality and understanding into the dialogue, and ultimately more peaceful attitudes".