The Tajiks constitute almost four-fifths of the population of Tajikistan . In the early 21st century there were about than 6,000,000 Tajiks in Tajikistan and more than 1,000,000 in Uzbekistan . The Tajiks are the principal ethnic group in most of Tajikistan , as well as in northern and western Afghanistan , though there are more Tajiks in Afghanistan than in Tajikistan .