The profit was lower than the $5.67 billion average of analysts' estimates compiled by the bank
Europe's biggest bank by assets said profit before tax came in at $3.21 billion for January-March, down from $6.21 billion a year ago
Aramco alone will be enough to move HSBC up two spots to 10th place on the main league table tracking stock offerings in EMEA
The Europe's largest lender, reporting results for the first quarter since the ouster of former chief John Flint, said adjusted pretax profit fell 12 per cent to $5.3 billion
Details of HSBC's investments in Serai were not disclosed
CEO said HSBC would invest $15-$17 billion in three years in areas including technology and China, while keeping profitability and dividend targets little changed
HSBC has been rebuilding its global equities operation since appointing Hong Kong-based Hossein Zaimi to run the business early last year
However, against expectations, firm rules out dividend hike and buybacks
The bank's shares rose 1.2% in Hong Kong on Monday on news of the appointment
$1 billion share buy-back takes HSBC's announced buy-backs since second half of 2016 to $3.5 billion
More than 90 per cent approved the executive pay report for 2015, after about 24 per cent of shareholders opposed it in last year's vote
HSBC is revamping the board after coming under pressure from shareholders unhappy about its performance