The troubled financial giant said in a statement it booked net loss of 3.2 billion euros ($3.6 billion) in the period from April to June, compared with bottom-line profit of 231 million euros a year earlier.
"We have already taken significant steps to implement our strategy to transform Deutsche Bank. These are reflected in our results," chief executive Christian Sewing said in a statement.
Earlier this month, Deutsche Bank said it would slash 18,000 jobs worldwide by 2022, retreat from most share trading activities and refocus on its German and European business, after decades attempting to compete with Wall Street titans.
The moves also aim to slash annual costs by six billion euros.
Related restructuring costs amounted to 3.4 billion euros in the second quarter and without them, Deutsche Bank would have made 231 million euros after tax, it calculated.
For some observers, the weak results confirmed fears that the bank had set itself overambitious profitability targets over the restructuring period.
"Even counting out the restructuring effects, they won't reach the target for 2019 of a return on tangible equity of four percent," analyst Andreas Plaesier of MM Warburg bank told AFP.
- Falling share price -
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The slump in profit was matched by a drop in Deutsche Bank's share price on the Frankfurt stock exchange, where it trailed the blue-chip DAX index to show a loss of 4.2 percent at 6.84 euros around noon (1000 GMT).
In April-June this year, Deutsche Bank's revenues fell six percent year-on-year, to 6.2 billion euros, in line with forecasts from analysts surveyed by Factset.
The biggest fall came at the investment banking division, which is set to suffer the deepest cuts during the restructuring, with share trading revenue in particular down 32 percent year-on-year.
Talks are underway with French bank BNP Paribas to sell parts of the trading activities, and more than 900 staff have already been laid off.
Outside share trading, the remaining businesses including the corporate and retail banks and asset management saw a gentler fall in revenues of 2.0 percent.
Across the group, Deutsche Bank reported a pre-tax loss of 946 million euros, compared with a 1.7-billion-euro profit in the same quarter of 2018.
But the bank said its restructuring was already bringing lower costs, which were down by four percent.
Over the whole year, Deutsche Bank expects falling revenues and a negative bottom line.
But management said cash and capital reserves are sufficient and they expect no major losses from a so-called "bad bank" set up to dispose of tens of billions of euros of risky assets.