This article collects together all accounts concerning Mahākassapa in the early Buddhist sources, both sutras and commentaries, in Pali and Chinese, with the aim of shedding light on his life. Our conclusions are as follows:

Mahākassapa's father was Kapila (or Nigrodha, both being Pali names) and his mother was Sumanadevī (Pali; Ch. Xiangzhi), wealthy members of the Brahmin caste from a town near Rājagaha in Magadha. Bhaddā Kapilānī, who later became his wife, was brought up in a Brahmin family living in Sāgalā in the country of Madda. Her father also had the name of Kapila, and her mother was called Sucīmatī. Both Mahākassapa and Bhaddā Kapilānī were of a religious cast of mind and did not wish to marry, but they did so at their parents' insistence; at that time Mahākassapa was twenty and Bhaddā Kapilānī was sixteen. After their children were born, they built a retreat (āśrama) in the forest near their town and retired there to live as forest-dwellers. Mahākassapa was then around thirty. Though this was a form of home-leaving, they had not yet fully renounced ties with their family. Their children were still young and though they had relinquished their actual upbringing to a foster parent, they could watch over them from their retreat. This life lasted twelve years. After that, Mahākassapa entered the life of a wandering ascetic (parivrājaka), the fourth of the four stages of life, a division that was just beginning to take shape in society. He then parted from his wife; he was around 42.

At about the same time, Sakyamuni also renounced the world and arrived at Uruvelā. He and Mahākassapa met around that time and found themselves in great sympathy with each other and each promised the other that if one became an arhat, the other would become his disciple. Sakyamuni was then 29, and Mahākassapa about thirteen years older. After Mahākassapa entered the life of a wanderer, he lived very much apart from the world and knew nothing of Sakyamuni's enlightenment nor his ministry centring on Magadha. Eventually though news of the formation of the Saṃgha in the area around Rājagaha and the Buddha's activities reached his ears. When too the Buddha happened to hear of Mahākassapa's circumstances, he went expressly from Rājagaha to the Bahuputtaka-cetiya to meet him. It was a longtime reunion. And as they had promised one another previously, Mahākassapa acknowledged that the Buddha was the master, and he the disciple. It is because of this background that Mahākassapa is said to have been originally of a non-Buddhist religion.

Mahākassapa's conversion must have been after the establishment of the ordination ritual characterized by the inclusion of the four-announcement ceremony, over a decade after the Buddha's enlightenment. This means the Buddha would have been around fifty at the time, and Mahākassapa well past sixty. This explains why Mahākassapa appears in the early Buddhist sources already an old man. Mahākassapa did not adapt to the life of the Saṃgha and continued his life of asceticism. Thus later he was given the epithet, "first in ascetic practices". However, because asceticism was principally an individual practice, living in the forest or wandering alone, and because Mahākassapa came relatively late to the Buddhist teachings, he was little known, compared with disciples like Ānanda, among those who knew only the life of the Saṃgha. Thus it was necessary that the Buddha show that Mahākassapa should be in no way despised, and that he was of equal stature to himself. This was the origin of a performance such as "sharing the seat".

Mahākassapa can be identified as an older type of Buddhist practitioner, whereas Ānanda is typical of the new type of disciple. Herein lay the seeds of a certain amount of discord. Ascetic practice (dhuta) itself had already come to be regarded by ordinary bhikkhus to whom the life of the Saṃgha was the norm as something alien to Buddhism. It was forbidden to recite even the four seeds of holiness before receiving the full precepts, and it is not surprising that the five strict rules for bhikkhus proposed by Devadatta (dwell all their lives in the forest, live only on alms, wear robes made from rags, live at the foot of trees, and obtain food by begging and refrain from eating fish or meat) should have been rejected.

Mahākassapa, as an older type of practitioner adhering to ascetic practices, was unable to countenance the ordination of women, and so did not have good feelings towards Ānanda, who brokered their entry, and the bhikkhunis in fact tended to keep their distance from him. This tendency is symbolized by Thullanandā Bhikkhuni. Mahākassapa's existence became better known within the Saṃgha in the final years of the Buddha's life. Sāriputta and Moggalāna were still alive at this time, but they both acknowledged Mahākassapa's superiority. Since they both died before the Buddha, Mahākassapa was inevitably left as the senior figure.

The Buddha had his eightieth birthday just before the rainy season retreat began in the Bamboo Grove on the outskirts of Vesālī. He was suffering a grave illness at the time. Though he survived for a while, it was clear that he was very weak. When the retreat ended and he left for his next destination, Kusinārā, there occurred an episode that foreshadowed his death three months later. Ānanda, sensing the Buddha's feelings, sent an urgent message to Mahākassapa in Rājagaha. Mahākassapa hurried to Kusinārā, but, already aged around 93 and facing a long journey, twice the distance of the route from Vesālī to Kusinārā, was unable to arrive before the Buddha died. The funeral took place seven days later, and Mahākassapa, though wearied from his journey, took charge of the council to collect together the teachings and regulations that the Buddha had left.