The loss of 8 cents per share compared to earnings of $76.6 million, or 34 cents per share, a year ago.
Second-quarter funds from operations fell to $313 million, or 96 cents per share, from $428 million, or $1.49 per share, for the same quarter last year.
Funds from operations are a key measure of operating performance for real estate investments trusts.
Simon took an impairment charge of $140.5 million, or 42 cents per share, during the quarter because of a decline in value of about 35 million shares it owns in British mall giant Liberty International.
Excluding the charge, Simon had funds from operations of $1.38 per sharea penny per share ahead of analyst expectations.
Quarterly revenue fell to $903.6 million, down from $922.9 million in the year-ago period.
The company declared a quarterly dividend, payable in cash and company shares, of 60 cents per share.
The company has sold new shares and notes to bolster an already strong balance sheet, CEO David Simon said in a statement. The company now has liquidity of $6 billion, including about $3 billion in cash.
"Our operating fundamentals remained sound, which resulted in a solid second quarter in the face of a difficult retail environment," Simon said.