The German team presented the findings during the annual meeting of the Radiological Society of North America.
Other experts say the results were not definitive because the team had not done a control study.
Researchers surmise that one of the leading causes of male infertility are varicose veins in the testicle or varicoceles.
Varicoceles are a tied-up network of blood vessels that result from blood circulation problems. An estimated 10-15% of men are believed to be suffering from this condition.
German researchers used a technique called embolization that involves inserting a small catheter into the groin and pointing it into the varicocele.
A tiny platinum coil and a special fluid are then injected through the catheter, to block off the faulty vein and curb blood flow through an alternative route.
The operation is minimally invasive and patients can go back to work the next day.
The operation was done on 173 infertile men, and results show that men's sperm motility and count improved within three months on average.
After the operation, 45 couples or 26% even reported pregnancy.
Sebastian Flacke, assistant professor of radiology at the University of Bonn in Germany, said: "This study confirms that varicocele repair can significantly improve sperm count and motility."
