Any loss at Germany's largest lender would break a streak of 15 consecutive quarters in the black in a setback for the bank's turnaround under CEO Christian Sewing.
The bank has warned it would set aside up to 1.3 billion euros ($1.42 billion) in the quarter for a long-running lawsuit claiming it underpaid for its purchase of its giant Postbank division.
The bank, which has strongly disputed the claims, declined to comment on the forecasts.
Deutsche publishes its earnings on July 24. The bank's actual results have exceeded analysts' expectations in recent quarters.
The new consensus forecast does show each of the bank's four key operating divisions posting profit before tax.
But the post-tax bottom-line loss attributable to shareholders could be around 280 million euros in the quarter, according to Reuters calculations based on the consensus.
That is wider than a 170 million loss foreseen in the bank's previous consensus forecast dated in May, and compares with a reported profit of 763 million euros in the second quarter of last year.
($1 = 0.9171 euros)
