Plot

Nenunnanu revolves around Venu (Nagarjuna) and his efforts to help Anu (Shriya Saran) patch up with her lover Arun (Subbaraju), the son of a rich businessman, who mistakes the Anu's relationship with Venu.

Venu is an orphan and a contractor at Vizag port. Anu is a student in classical singing. Sruthi is Anu's friend. Anu makes an attempt to elope with her boyfriend Arun. Arun is the son of business tycoon JP. JP sends police across to nab Anu. As police nab Arun, Venu rescues Anu. Anu's father disassociates himself from his daughter. Then Venu takes Anu to his place and gives assurance. Venu finds out where Arun is and gets Anu married to him. JP tells his son that Venu and Anu have an affair as they live together in the same house. Arun gets suspicious about Anu's character and leaves the marriage venue immediately after the marriage. Anu is back in Venu's place. Venu is in the mission of locating Arun and convince him to come back to Anu. As Anu and Venu spend more time together, they get closer. Venu never takes advantage of it and treats Anu like a good friend. Anu pines for Arun but learns that Arun will marry the Minister's daughter. Venu goes to the engagement venue and tries to stop Arun from getting engaged. Anu comes and slaps Arun, saying that their marriage is over. She goes for a singing competition with Venu accompanying her. She wins the competition as well as her father's love. Arun, meanwhile tries to kill Venu but accidentally gets an electric shock. He gets paralyzed for life. JP seeks revenge. Sruthi falls for Venu. Anu goes back to her father's house and now, being unmarried, thinks over her relationship with Venu. She realizes that she loves Venu. Venu, too, reveals among his friends that he loves Anu, but will never tell her. Sruthi overhears both Anu and Venu's feelings and decides to sacrifice her love for Venu. Her parents decide to get her married to Venu. Sruthi refuses to marry Venu and tells them everything. Sruthi's mother gets angry and asks Anu to arrange her daughter's and Venu's wedding. Anu gets heartbroken but thinks that it's better for everyone. Sruthi goes to Venu and tells him that Anu, too, loves him. Anu is kidnapped by JP and his goons.

Venu goes to save Anu. After a big fight, he is able to defeat JP and save Anu, but Anu is stabbed. Sruthi comes and she takes Anu to the hospital. Venu comes to the hospital later. Anu asks the doctors to allow her to meet Venu before treating her. Anu and Venu confess their love for each other. Anu is successfully operated upon and finally united with Venu, with everyone's, including Sruthi's mother's, wishes. Then Venu marries Anu and lives happily ever after.