Mann Mayal depicts the story of Manahil (Maya Ali) and Salah-ud-Din (Hamza Ali Abbasi), who are neighbors and Ali Baig's sister Rabia (Aiman Khan) is a friend of Manahil. Salah-ud-Din is ambicious for studies but is however asked by Manahil's father to give tuition to Manahil because of her low grades. Both fell in love but Ali Baig refuse to marry Manahil due to their social-class status and due to fear of rejection from her family. Manahil's parents accept the proposal of Mikaeel who is unknown to Manahil's family is a spoiled-habitual person. Salah-ud-Din says last goodbyes to Manahil before her marriage only to end up in allegation that he took her, he then settled things out and left for karachi to work at his friend Iftis' (Vasay Chaudhry) firm, where he met Ifti's father Rehman (Talat Hussain) who is dying of cancer and is treated poorly by his daughter in law "Cookie" (Arjumand Rahim) and housekeeper Jamil (Saleem Mairaj). Salah-ud-Din and Rehman develop a close bond and they confides in each other.[10]

Despite her family’s opposition, Manahil leaves her home and family for Salah-ud-din u but is left empty handed, filled with regret and remorse. Series then takes the leap of 3 years with Salah-ud-Din returning and finds everything changed. The latter half of the series shows the trials of Mannu and Ali Baig's fate of love, and his feelings for Manahil. He also found out that Meekail tortures' Manahil and her silence to torture to punish herself as she promised to Salah ud din3 years ago. Jeena is also introduced who works with Salahudin as his colleague and later fell for him. Other recurring roles include Manahil's parents Saba Hameed as Saliha and Naeem Tahir as Javed, Ali Salah ud din's parents Ismat Zaidi and Shehryar Zaidi and Laila Zuberi as Rahila and Mehmood Aslam as Shahad who plays Mikaeel's parents,[9] appears throughout the series.