Tatar, a pro-Turkey candidate, won with 51.74 percent of the vote against pro-unification incumbent Mustafa Akinci, who garnered 48.26 percent.
“I congratulate Mr. Ersin Tatar, who was elected the President of the Turkish Republic of Northern Cyprus, on behalf of myself and the Turkish Nation,” Erdogan wrote on Twitter.
Erdogan has made no secret of his support for Tatar, who ran on a Turkish nationalist ticket, at times getting flak for his overt closeness to Ankara.
Defeated incumbent Akinci raised doubt over the veracity of the results but congratulated Tatar over the victory and announced the end of his 45-year political career, news agency TAK reported.
The Eastern Mediterranean has become a flashpoint in regional tensions after the discovery of large underwater gas reserves. Turkey has played the most proactive role, claiming territorial rights over vast swathes of waters, drawing up deals with Libya and increasing prospecting around the divided island of Cyprus, provoking a plethora of criticism from European nations.