According to 2001 census, the total population of Attappady is 66,171, which includes 27,121 (41%) Scheduled Tribes and 3024 (4.5%) Scheduled Castes. The Scheduled Tribes belong to the Dravidian clans of Irula, Muduga and Kurumba. Out of the total population of 66,171, 55% is contributed by general category. The tribals constituted a majority of the population up to 1961; but are now in minority, for settlers from outside outnumber them. 

AHADS Hamlet Survey 2002
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The Kurumba tribes are considered as the earliest tribal inhabitants of Attappady. When the Baduga started colonizing the Nilgiris, these people moved down to the Attappady valley. They are the smallest among the three tribal groups of Attappady. After an initial period of nomadic life, they must have taken up shifting cultivation; their main occupations being hunting and gathering. Once their hamlets were distributed in the valleys of river Bhavani and its tributary Varagar. Now there are 19 hamlets spreading across the catchment area of Bhavani river. However, all these people have their settlements inside the forest, and until recently they had hardly any contact with the outside world.

The Kurumba have the same social hierarchies that the other groups observe, with Moopan as the head of a settlement. There are reports of a few inter-tribe relations between Kurumba and Muduga, as some of the Kurumba have married among Muduga tribes. They occupy the headwaters of the major streams in the upper reaches of the mountains, and have been shifting cultivators. They practice dry-land farming in the lands cleared in the forest areas. In addition, they also depend upon the collection of non-timber forest produces for generating income. Due to their intricate knowledge of the forest terrain, they have been misled by vested interest groups and have been used to cultivate Ganja (cannabis) inside the forest areas. The Forest and Excise departments have constantly raided the areas and such situations lead to social unrest. Adopting the approach of persuasion and intervening in their social development, they are being slowly weaned away from such practices.

Muduga are the second largest tribal community in Attappady, covering 24 hamlets. Most of the Muduga hamlets are settled in the western Attapady, mostly in the proximity of Bhavani river.

It is believed that the Muduga were the original inhabitants of Coimbatore plains and later moved westward due to persecution and exploitation by more dominant communities. They are dry-land farmers, sowing crops such as ragi, thuvara, chama etc. They have more contact with the migrated settlers from the plains of Tamilnadu and Kerala. Literacy rate of Muduga is relatively higher among the tribals. The growing contact between Muduga and settlers has influenced their culture.

Irula are the numerically dominant and relatively advanced among the three tribal groups in Attappady. They probably occupied this area after the Kurumba and Muduga. They mostly inhabit the eastern half of the valley and are found residing in 144 settlements, distributed over all the three Panchayats of Attappady. They once were shifting cultivators, but due to land alienation over decades, they were forced to practice settled agriculture and plough cultivation. At present, those who possess small plots of land near their hamlets perform dry land agriculture, mainly indigenous grains and cotton. However their major source of income is wage labour.

Non-tribes residing near the Coimbatore border must have established early contacts with the Irula in Attappady and mainly the Tamil Goundan began to migrate to the eastern side in the 1920s. Although they came mainly for agriculture, at first they did not settle down in the area. Instead, they entrusted the agriculture jobs to the Irula and only collected the produce. Towards the late thirties, however, the Goundan began to settle in Attappady and cleared forests. The Kururmba and Muduga who occupied the interior areas were not affected significantly by these early settlements.  

However, from the 1940s to 1980s, a large number of people from the plains of Kerala moved into the Attappady valley, mainly to exploit forest wealth as well as to use the cultivable lands. It was only after an all-weather road from Mannarkkad to Malleswarankovil was constructed in 1946 and later extended to Coimbatore, that the pattern of migration to the area changed. The pace of migration into the area increased from about 800 persons per year from 1951-1961 to over 2,000 per year during 1961-1971. 

The migrants, who settled down in the drier zones in the three village- Agali, Pudur and Sholayur, were from the neighboring areas of Tamil Nadu. The migrants of Kerala origin who came mostly from the plains settled in the high rainfall areas such as Karara, Chittur and Sholayur. The cultivation practices of the migrant groups determined the choice of localities for settlement. Of the Malayali migrants, more than 50 percent were from central Travancore and around 30 percent from the plains of Palakkad. They adopted the crops and cultivation practices with which they were familiar. Such an adoption of ecologically incompatible cropping systems, along with massive forest clearance, has been the major cause of degradation of the ecology of Attappady.