Fawzia Koofi, the only woman taking part in negotiations with the Taliban escaped a shooting attack “without serious injury”.
The attack was a “cowardly and criminal” attempt to disrupt the Afghan peace process, the US envoy has said.
Ms Koofi was shot in the right arm while travelling with her sister.
Ms Koofi, an outspoken critic of the Taliban who was returning from a meeting in the northern Parwan province when she was attacked near the capital Kabul, could undermine the peace process.
“Worrying pattern of targeted attacks that can negatively impact confidence in peace process,” the chief of Afghanistan’s Independent Human Rights Commission, Shaharzad Akbar, wrote on Twitter.
The Taliban have denied they were behind the attack, which came as the two sides prepared for talks.
The militant group has previously refused to negotiate directly with the Afghan government, but agreed to take part in the talks aiming to end almost two decades of conflict after reaching an agreement with the US in February.
As part of the agreement, the Afghan government had to release 5,000 Taliban prisoners. On Thursday, it began releasing the last 400 militants. Talks are expected to start in Qatar after the final prisoner is released.