The drop triggered a half-hour suspension of trade in EFG.
QInvest would have pumped in $250m for a 60 percent stake.
On Wednesday, EFG, one of the largest investment banks in the Middle East, said it plans to cut costs, sell non-core assets, and return cash to shareholders after the tie-up plan failed.
The two parties said in a joint statement that the deal had been terminated due to lack of regulatory approval from Egypt and that they would continue to operate as independent entities going forward.
In a separate statement to the Egypt bourse EFG said it will seek to reduce its "expenditure structure" by 35 percent to 500 million Egyptian pounds ($72.11m) in 2014 from 780 million pounds for 2013.