Net profit totalled 28.5 billion kronor (3.13 billion euros, 4.05 billion dollars), down from 43.8 billion in 2005, the Swedish group said in a statement.
In the fourth quarter alone, net profit fell by 14 percent to 10.5 billion kronor from the same period a year earlier.
Investor said the value of its share holdings grew by 19 percent in 2006 owing to the strong economic cycle and positive restructurings undertaken by the companies in its portfolio.
As of 31 December 2006, net asset value amounted to 159.3 billion kronor, compared to 133.9 billion at the end of 2005.
Investor, which holds stakes in more than 130 companies worldwide, saw its net asset value per share climb from 175 kronor to 207 kronor at the end of December.
Among Investor’s main holdings are Swiss-Swedish engineering group ABB, Anglo-Swedish pharmaceutical group Astra Zeneca, Swedish bank SEB, industrial equipment manufacturer Atlas Copco, and the world leader in telecoms networks, Ericsson.
Investor, which is controlled by the influential Wallenberg family, is also one of the main shareholders in Swedish truckmaker Scania.
In its statement on Thursday, Investor reiterated its rejection of German industrial group MAN’s hostile bid for Scania, saying it only saw potential for a friendly collaboration between the two truckmakers.