The bank holding company said profit fell in the fourth quarter to $668 million, or 76 cents a share, from $842 million, or 93 cents a share.
But the results did beat the current analysts' earnings expectations of 75 cents a share.
WaMu said the lower fourth-quarter profit fell primarily due to several unusual items in that period, including a reversal of reserves for loan and lease losses.
However, for the full year, in which net income fell to $2.88 billion, or $3.26 a share, from $3.88 billion, or $4.21 a share, the company also cited lower securities gains and lower home loan mortgage banking income.
Fourth-quarter net interest income rose 6% to $1.85 billion.
Profit at the company's mortgage banking segment was $138 million in the fourth quarter compared with $270 million in the third quarter and $232 million in the year-earlier quarter.