The chief minister cast his vote at the remote Chenkompara polling station in Ampati constituency in the afternoon, they said.
Sangma is seeking re-election for the fifth time from his home constituency in Ampati, the officials said.
"Citizens of Meghalaya do exercise your voting rights in a responsible and judicious manner. Counting on you all for peaceful elections throughout the state," the chief minister had tweeted earlier during the day.
"We have done our best. We have showed the vision for the state. I am confident people will vote for change. It is now for the voters and I hope people turn out in large number," Conrad Sangma told PTI over phone soon after casting his vote.
Meghalaya Governor Ganga Prasad cast his vote is Oakland polling station in North Shillong constituency in the morning. The polling station has been designated as a model polling booth by the Election Commission.