The current-account balance, the broadest measure of a country's trade and financial exchanges with the outside world, showed a surplus of €1.357 billion ($1.8 billion) for the first half of 2013, the central bank said.
That contrasted sharply with a shortfall of nearly €17 billion in the same period last year.
"This change mainly reflects the notable improvement in the trade deficit, followed by an improvement in returns on investments and services," the Bank of Spain said in a statement.
It was the first time Spain had recorded a surplus for the first half of the year since current records began in 1990, and its first half-yearly surplus since 1997.
Spain's conservative government says the economy, the eurozone's fourth-biggest, is heading out of its two-year recession. The latest growth figures showed the pace of economic contraction slowed in the second quarter.
Friday's data also indicated strengthening investor confidence in Spain, which last year turned to its eurozone partners to bail out its banking sector but resisted pressure to seek a full sovereign bailout.
Spain recorded an investment inflow of €39.8 billion in the first half of 2013, compared to an outflow of €225 billion in the same period last year.
In trade, the shortfall of exports to imports was less in the first half of 2013, shrinking to €2.71 billion from €15.65 billion in the first half of 2012, the bank said.
Spain's services sector increased its surplus to €17 billion from €15.19 billion a year earlier.
In another key sector, tourism, the surplus grew by 4.7 percent to €13.88 billion. The industry reported a record number of foreign tourists coming to Spain in July this year.