US fund manager BlackRock, which manages more than $US4.1 trillion ($A4.59 trillion) in assets worldwide, has built up a five per cent stake in casino and hotel operator SkyCity Entertainment Group.

BlackRock Investment Management (Australia) on Wednesday declared it held almost 29.1 million shares, or 5.01 per cent, of SkyCity, which owns the Adelaide Casino.

It makes it the third fund manager to build a substantial investment in the Auckland-based company after fund managers Lazard Asset Management Pacific and Investors Mutual, which made similar announcements last August.

BlackRock built up the stake from September, according to a substantial shareholder notice.

SkyCity shares have gained 4.3 per cent this year.

Last month, SkyCity warned that its first-half profit would fall as a strong New Zealand dollar versus its Australian counterpart weighs on earnings, due to its Darwin and Adelaide casinos. The company is expected to release its first-half earnings on February 12.