The indirect talks between the Syrian government and opposition will resume in the Swiss city on April 13.
De Mistura planned to meet senior Iranian officials, including Deputy Foreign Minister Hossein Amir-Abdollahian.
The UN envoy traveled to Damascus on Sunday and met with Syrian officials there. He said there that the upcoming round of intra-Syrian dialogue would be "crucially important."
Amir-Abdollahian was speaking to envoy Staffan de Mistura, who arrived in Tehran after holding meetings with Syria's foreign minister in Damascus on Monday.
"One of our main concerns in Syria is the increasing activities of armed groups in recent days and the increase in breaches of ceasefire that can harm the political process (of peace talks)," he said.
The last round of the UN-backed peace talks for Syria came to a halt on March 24 over disagreements on the role of President Bashar al-Assad in Syria's future.
The foreign-backed Syrian opposition says Assad must step down before a transitional government can be established.
Last month, Syrian Foreign Minister Walid Muallem reiterated that Syria "will not talk with anyone who wants to discuss the presidency," adding, "Bashar al-Assad is a red line."
The West and its allies in the Middle East say Assad cannot be part of a future government in Syria. Iran and Russia insist that the Syrian people must decide on their future.
Syria has been gripped by civil war since March 2011.
According to a February report by the Syrian Center for Policy Research, the conflict in the Arab country has claimed the lives of over 470,000 people and displaced nearly half of its pre-war population of about 23 million within or beyond its borders.
Editor's note: This article has been edited from the source material
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