Rajiv Gandhi's wife Sonia and his two children, Rahul and Priyanka, who is also the Congress General Secretary, paid tributes at his memorial, Veer Bhumi, here.
Former Prime Minister Manmohan Singh and former President Pranab Mukherjee were also present at Veer Bhumi along with other senior party leaders.
Modi, who was recently criticised for his remarks against Rajiv Gandhi while campaigning for the recently concluded Lok Sabha elections, said in a tweet: "Tributes to former PM Shri Rajiv Gandhi on his death anniversary."
After visiting Veer Bhumi, Rahul Gandhi said in a tweet: "My father was gentle, loving, kind & affectionate. He taught me to love & respect all beings. To never hate. To forgive. I miss him. On his death anniversary, I remember my father with love & gratitude."
West Bengal Chief Minister Mamata Banerjee also remembered the late leader, saying: "Solemnly and very fondly remembering former Prime Minister Rajiv Gandhi on his death anniversary."
Overseas Congress chief Sam Pitroda, in a series of tweets, said: "Today is the day to pay respect to this great leader who dreamed of India in the 21st century and at the same time reflect on his contribution to India."
Pitroda worked with him as an advisor on technology missions.
"Rajiv Gandhi's life was taken away at an early age by a terror attack. His loss left a huge vacuum in politics, leadership, and development in India," he added.
Rajiv Gandhi was assassinated on May 21, 1991, by a female LTTE suicide bomber, who greeted him at a rally in Tamil Nadu's Sriperumbudur town with a bomb strapped to her chest.
He served as the sixth Prime Minister of India from 1984 to 1989. He took office after the 1984 assassination of his mother, Prime Minister Indira Gandhi, becoming the country's youngest Prime Minister at age 40.