The move is part of the new pro-business leader's push for faster economic growth.
The Central American country has been analysing its inclusion in the group - which was formed in 2011 by Chile, Colombia, Mexico and Peru - for more than a decade, though some former governments have rejected it.
The Pacific Alliance seeks stronger economic and commercial ties, based on principles of free movement of goods, services and capital while targeting nations clustered around Asia's Pacific coast, home to some of the world's fastest-growing economies.
Chaves, a maverick economist, took office in May.
Speaking to reporters, he explained that Costa Rica's main objective is to open the country "to the east of the world, where we have little trade and we have ambitions to enter a trans-Pacific agreement, to get closer to countries like China".
Costa Rica, whose economy is expected to grow 3.4 per cent this year, has existing free trade agreements with China, Singapore and South Korea.
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