Polling stations across the European Union member nation opened at 7am (0400 GMT) on Saturday, with voting set to end at 10pm.
Final results are due in the early hours of Sunday.
Opinion polls released on Friday showed that support for the ruling People's Party - and its partners the Greens and Farmers Union and Latvia's First Party - had risen to 32.9 per cent compared with 30.8 per cent in a poll released a week ago.
And although support for opposition groups rose slightly, they remain disunited with support only in single digits.
Analysts have said that with the election lacking major issues, voters would back the incumbent administration, which was seen as a safe pair of hands to nurture prosperity in one of the EU's fastest-growing economies.
Pollsters said support for the coalition was enough for it comfortably to secure more than 40 seats in the 100 seat parliament.
Aigars Kalvitis, the prime minister, has said that if he wins his government will continue to build close relations with the West and other EU states.
He said he will also press for his country to adopt the euro as its currency.
"I think Latvian support for EU membership is quite high. In meetings with the people I sense they are much more comfortable than before," he said.
"I'm quite sure there will be high participation in this election."
Latvia joined the EU in 2004.