(Removes incorrect day of week in second paragraph)
* Investment gains slow to 1.5 pct in latest quarter
* Fund achieved 3.7 percent gain in last fiscal year
* CEO says Brexit uncertainty to be protracted
By Matt Scuffham
TORONTO, Aug 11 (Reuters) - The Canada Pension Plan Investment Board warned on Thursday of more uncertainty following Britain's decision to leave the European Union after the vote curbed gains in its investments during the last quarter.
The CPPIB, which manages Canada's national pension fund, reported gross investment returns of 1.5 percent for the first quarter ended on June 30, a slowdown from the 3.7 percent gain it achieved in the fiscal year to March 31.
Chief Executive Officer Mark Machin, who is British, said global investors had experienced ongoing volatility during the quarter, generating mixed results across major equity markets.
In an interview, he said there had been "very extreme volatility" immediately after the June 23 "Brexit" vote, followed by a rebound that was only partially reflected in first-quarter results.
Machin said the decision would lead to "protracted" uncertainty as Britain negotiates its exit from the EU.
"We're obviously watching the rest of Europe as well," he said. "I think it's unlikely we're going to see a sudden end to very difficult macroeconomic management of economies by central banks and governments."
Machin, a former medical doctor and Goldman Sachs (NYSE:GS) veteran who joined CPPIB four years ago to oversee its international investment activities, became CEO in June. He replaced Mark Wiseman, who stepped down ahead of taking a senior position with BlackRock Inc (NYSE:BLK) BLK.N , the world's largest asset manager.
The CPPIB, which invests on behalf of 19 million Canadians, has diversified internationally and into alternative asset classes such as infrastructure and real estate to offset the impact of record low yields on government bonds and volatile equity markets. Machin said that strategy would continue.
"We have 25 different investment groups which are all out looking for opportunities," he said, "and their job is to find those dislocations that are thrown up and take advantage of them."
The fund ended the quarter with net assets of C$287.3 billion, compared with C$278.9 billion three months earlier.
Machin said the increase stemmed primarily from a positive performance from fixed income investments, gains from equity investments in Canada and the United States, and the performance of its private investments.
About a third of the fund's investments remain in public equity markets.
(Editing by Chizu Nomiyama and Lisa Von Ahn)