The shares were sold for a total of 95.8 million pounds ($194 million).
Nasdaq, which had owned about 30 percent of the London exchange following a failed bid to take over the LSE, also sold 56 million LSE shares on Thursday.
Qatar and Dubai are now the two biggest shareholders of the LSE, holding almost half of the world’s third-largest stock exchange.
Borse Dubai agreed on Thursday to buy a 28 percent stake in the LSE from Nasdaq. Qatar Investment Authority (QIA), the investment unit of the Qatar government, bought 20.86 percent of the LSE, according to a regulatory document filed on Thursday.
Nasdaq and Borse Dubai also agreed to buy stakes in one another in a deal to create a group of exchanges with unprecedented reach, linking the United States, Europe, the Middle East and Asia.
Reporting by Mark McSherry