"Our thanks to the emir for his generous gesture of restoring the revoked citizenships," Islamist opposition MP Mohammad al-Dallal tweeted after a meeting with Emir Sheikh Sabah al-Ahmad Al-Sabah.
Several of the 14 MPs who attended the meeting confirmed that the oil-rich Gulf state's ruler had ordered the citizenships to be restored.
The Kuwaiti government in mid-2014 stripped at least four opposition figures and dozens of their family members of their nationality as part of a crackdown on dissent.
Those affected included Islamist former opposition MP Abdullah al-Barghash and more than 50 members of his extended family.
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They also included former spokesman of the opposition Popular Action Movement Saad al-Ajmi, who was later deported to Saudi Arabia.
The owner of the opposition-linked Alam Al-Youm newspaper Ahmad Jabr al-Shemmari and Islamist preacher Nabil al-Awadhi also lost their nationality.
Several of those affected sued the government.
The move to restore their status comes after a November snap election in which opposition groups participated after a four-year boycott, winning almost half of the 50 seats.
Kuwait has a native population of 1.35 million, many of whom became citizens through naturalisation.
The emirate also has 3.1 million foreign residents.