Dosti is the story of Ramnath or Ramu (Sushil Kumar) and Mohan (Sudhir Kumar). Ramu’s father Mr. Gupta, a factory worker, dies in an accident. When the factory refuses to pay compensation, his mother passes out in shock. Ramu is injured in an accident, and he becomes crippled. Thrown out of his home, crippled, and penniless he roams around the streets of Mumbai. Here he comes across Mohan, a boy who is blind and has a similar tale of woe. Mohan comes from a village, and he lost his sight at an early age. His sister, Meena, had migrated from the village to find work as a nurse so that she could pay for her brother’s treatment. Mohan left the village after his mother passed away. Ramu is good at playing the harmonica, while Mohan is a good singer. They team up and sing songs on the roadside, earning money from passers-by. Ramu wants to finish his studies, and both of them befriend a small girl, Manjula (Baby Farida), who is the sister of a rich man Ashok (Sanjay Khan). Manjula suffers from a terminal disease, and both the boys hope she would help them out. Ramu and Mohan visits Manjula and asks. as a loan, sixty rupees which is required for Ramu's admission in school. But Manjula's brother rebuffs them and gives only five rupees. Feeling insulted, Mohan decides that he will raise the money by singing, which he successfully does. Ramu is admitted in the school after performing brilliantly in entrance test (he scores 294 out of 300). They move to a new house in a slum after someone tries to steal their hard earned money in their earlier shelter. Their new neighbour is Mausi, who lives with her teenage daughter and school going son, Chandu. Mausi treats them as her own son. In school, Ramu excels in studies despite being a a regular target of ridicule of richer students who does not consider him their equal and often degrades him for being a street beggar.The headmaster and teacher Sharmaji takes Ramu under their wings. Sharmaji has also declared himself as guardian of Ramu. During a visit to Ramu's house, Sharmaji notices that the neighbour hood is not fit for study and suggests Ramu to move in with him, but Ramu does not leave Mohan.Meanwhile, one day while singing, Ramu hears someone (Ashok, Manjula's brother) calling out to Meena and rushes to embrace her long lost sister. But Meena is ashamed that Mohan has become a beggar and refuses to recognise him. Meena is looking after Manjula and there is a budding romance between her and Ashok. However, soon Meena confesses to Ashok. Ashok is sorry for her and consoles her that soon she will be together with her brother. Manjula dies the day Ramu and Mohan visit her to tell about Ramu's admission. Ashok brings Mohan home one day and gives him Manjula's chime as her remembrance.When he tries to tell Mohan about Meena, Mohan thrashes out in rage and says that he consider himself alone in this world, save for his friend Ramu. Soon after, Ramu gets in trouble with some street ruffians and as a result is mistakenly arrested by police during a burglary. Sharmaji goes to police station and bails Ramu in condition that he will live with Sharmaji and keep no contact with Mohan. Mohan is heartbroken and roams the streets singing. Sharmaji suddenly dies, leaving Ramu shattered. Ramu decides not to appear for the final exam as he is not able to pay the requisite fees in absence of Sharmaji. Hearing this, Mohan decides to realise the money once again by singing in streets in spite of his ill health. He successfully earns the money and deposit the fees without Ramu knowing, but himself falls prey to illness and is admitted in hospital. In hospital, without telling him, Meena cares for her and Mohan recuperates. Ramu comes first in the exam and comes to know of Mohan's sacrifice. He rushes to Mohan in hospital where Mohan forgives him. The doctor tells Mohan about Meena and Mohan forgives her also. The movie ends with all of them in a loving embrace.