Poudel, a common candidate of eight-party alliance that included Nepali Congress and the CPN (Maoist Center), received the vote of 214 lawmakers of parliament and 352 provincial assembly members.
Backed by ruling alliance and supported by nine political parties, Poudel defeated veteran communist leader Subash Chandra Nembang who was solely backed by the CPN-UML.
"Hearty congratulations to my friend Ram Candra Poudelji for being elected as the President," Nepali Congress chief Sher Bahadur Deuba tweeted.
Poudel, 79, the former speaker and deputy prime minister and veteran democratic leader has been active in politics since six decades.
The total number of voters for the election of the President is 882, consisting of 332 Members of the Parliament and 550 members of the provincial assemblies of the seven provinces.
Shaligram, the spokesperson of the Election Commission, said 518 Provincial Assembly members and 313 Members of the Federal Parliament cast their votes in the presidential election.
This is the third presidential election in Nepal since the country became a republic in 2008.